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COPYRIGHT DEPOSIT. 



MANUAL or AGRICULTUKE 

FOR SECONDARY SCHOOLS 



STUDIES IN SOILS AND 
CROP PRODUCTION 



BY 



D. O. BARTO, B.S. 

INSTRUCTOR IN SECONDARY SCHOOL AGRICULTURE 
COLLEGE OF AGRICULTURE, UNIVERSITY 
OF ILLINOIS 



WITH INTRODUCTION BY 



E. DAVENPORT, M.Agr., LL.D. 

DEAN OF THE COLLEGE OF AGRICULTURE 
UNIVERSITY OF ILLINOIS 



BOSTON, U.S.A. 

D. C. HEATH & CO., PUBLISHERS 

1910 



^4*- 



Copyright, 1910, 
By D.- C. Heath & Co. 



(gCI.A25(.>;^^ 



INTKODUCTION 

We are making educational history these days at a rapid rate, 
and not the least important chapter is on the new status of affairs 
industrial. At last agriculture is coming into its own, and it will 
not be many years until this subject will have taken its place in 
the American secondary school system as it is now taking its place 
within the colleges and universities. 

This is not only because agriculture employs the time and 
absorbs the lives of a third of our people and feeds us all ; it is 
not only because the future and the development of every people 
is limited by the production of the soil it occupies ; it is not only 
because it is expedient from the community standpoint that this 
subject should be studied by young people and developed by sci- 
ence ; it is largely because, after all, the subject-matter of agricul- 
ture, its method and its outlook, are exceptionally valuable in 
their influence upon the individual, educationally. 

Elsewhere ^ I have written, "It is dangerous to attempt to edu- 
cate a live boy with no reference to the vocational," and I might 
add that it is dangerous to the community, as it is unprofitable 
to the individuals, to fill our schoolhouses day after day with young 
men and women to study seriously all the problems of life except 
the one supreme problem of how to make a living, a large and sig- 
nificant portion of which problem from the racial standpoint is com- 
prised within the range of farming and farm life. 

The introduction of agriculture into the secondary schools has 
been delayed from the same causes which have retarded the devel- 

1 " Education for Efficiency," Chapter I, Heath & Co., 1909. 



iv INTRODUCTION 

opment of the agricultural colleges ; viz., want of teachers, igno- 
rance of suitable matter and methods, and the lack of an adequate 
literature both for reference and for text. 

It has taken the colleges more than forty years to overcome, 
even measurably, this inherent handicap upon a new academic 
subject, rendered more serious in this case because of peculiar 
ancient traditions regarding the ideals and the scope of education. 
In the last five years, however, the future of these colleges has not 
only become assured, but their success has engendered the demand 
that agriculture be also taught in schools other than colleges, not 
only to relieve congestion there, but more especially to bring to 
the masses of people where it will do the utmost possible good 
the recent findings of science regarding the maintenance of the 
food supply of a people, on the one hand, and that standard of 
life and living that find their highest exemplification in a properly 
developed country life. 

The next place for agriculture, therefore, is in the secondary 
schools, and their period of trial ought to be far more brief than 
that of the colleges. This is because, though teachers are yet 
to be produced, the colleges, in their experience, have learned 
much, both of matter and of method, that can be transferred 
directly into the secondary school, particularly the well-organized 
high school with a country constituency. These same colleges, 
too, in cooperation with the normal schools, are able to produce, 
and are already producing, eminently qualified teachers. 

From now on the supply of teachers will come along in natural 
response to a demand that takes all promising candidates at 
maximum salaries, so that the great business of the immediate 
future, and one that must largely be left to the enterprise of indi- 
viduals and the initiative of far-seeing publishers, is the production 
of suitable reference and text-books, for no subject is teachable 
till it has an adequate literature. 



INTRODUCTION V 

These books are now springing up, as if by magic, from all 
sorts of unexpected places. The surprising fact is that there are 
so many, and the still more surprising fact is that they are so 
good — better by far, most of them, than the best that were avail- 
able for college purposes when the writer was a student. 

Too many of these books, unfortunately, are confessedly " ele- 
mentary," whereas it is not elementary agriculture that the farmer 
most needs. What he wants is instruction in the elementals of 
agriculture. It is the fundamentals of the subject that need to 
be emphasized and taught, and fortunately many of these books 
belie their titles and are not, after all, " elementary," but elemental. 

Many of these texts cover the entire range of agriculture, though 
necessarily in abbreviated treatment. There are those who believe 
that when agriculture is fully introduced as a secondary school sub- 
ject, it will consist, as in college, not of one but of several courses, 
each with its distinctive and separate text. Such a text the author 
has attempted to produce, dealing with a somewhat restricted and 
altogether definite field — the soil and the principal crops of the 
northern states. 

Most books heretofore prepared have been repositories of infor- 
mation to be studied and recited like other subjects. This book 
is distinctively a laboratory manual, the belief of the author being 
that the student should be led to study agriculture at first hand, 
and that his impressions as well as his knowledge of the subject 
should be gained through the most intimate personal contact, 
remembering always that it is the science of agriculture and not 
its art or handicraft that is teachable in our schools. 

The author is eminently qualified to treat the subject he under- 
takes. A farmer by instinct, with a long and successful career 
as a teacher in secondary schools, he took the agricultural course 
at the University of Illinois in the ripeness of full maturity. He 
has since that time given his exclusive attention to the adaptation 



vi INTRODUCTION 

of agriculture to secondary instruction, for which he has enjoyed 
exceptional advantages through his connection with the agricultural 
extension department of the university. He therefore brings to 
this book not only the instincts of a farmer, but the knowledge 
of the specialist and the ripeness of judgment of a mature and 
successful teacher. 

It is to be hoped that if this attempt shall prove successful, 
either this author or others equally able and equally willing to 
perform a labor of love will extend the laboratory manual idea 
to other fields of this most fascinating subject. 

E. DAVENPORT. 



PREFACE 

Theoughout the country to-day many schools of secondary 
grade are expressing a desire to add to their present curricula of 
studies courses of instruction in agriculture ; but they are in doubt 
as to the character and extent of the work which would be possi- 
ble or advisable for them to olfer in this subject. 

While a considerable number of elementary books in agriculture 
has been written in recent years, few, if any, of them were pre- 
pared for high school grades, and do not assume to compare in 
the character of matter presented or in their thoroughness of the 
treatment of the subject with texts in the other sciences taught 
in high schools. 

Agriculture is now recognized as embracing so large a field, with 
so many different divisions and special interests, that no single 
book within the proper bounds of a high school text could pretend 
to compass the whole subject. The work should be presented in 
separate courses which may be taken by classes either in the order 
of their natural sequence, or a selection can be made of those 
courses most directly related to the particular agricultural interests 
of the communities where the schools are situated. 

There are many excellent books on the various topics included 
in each department of agriculture, and a great wealth of agricul- 
tural information has been published in bulletin form. All of 
this is available matter for reference and should be of much value 
to teachers and students in their work ; but as yet there are no 
texts in agriculture that have been prepared to meet the special 
needs of high school courses. There is no question, however, but 



viii PREFACE 

that the urgent demand for such texts will call forth in the near 
future many good books, and in the meantime much may be done 
with the material now at hand in making a beginning in the work 
of secondary school agriculture. 

The purpose of this Manual is to outline a course of study in 
agriculture, covering at least one year's work, which shall be of 
high school grade, and shall offer training in sciences comparable 
to that furnished by the other science courses in good high schools. 

The writer believes that all of the work in agriculture taught 
in our high schools should be of such character that it will appeal 
to the practical farmer as real agriculture, possible of application to 
actual conditions and closely related to the affairs of the homes and 
the farms of the community. In addition to this it should possess 
such educational value, both in its content and in its opportunities 
for training in scientific methods and habits, as to justify its place 
in the curriculum of any good high school. 

The work as outlined in this course is confined to studies in 
soils and crop production. Since the growing of crops is the basis 
of all farming operations and every form of agriculture is inti- 
mately associated with the cultivation of the soil, it seems best 
to make this work the foundation for the courses in agriculture 
to be taught in high schools. 

Then, following this, a study of the breeds and types of the 
most important farm animals and something of the laws of breed- 
ing and improvement of stock, a study of methods of feeding, the 
principles of nutrition and a comparison of the nutrient values 
of the different foodstuffs produced and used on the farm, the 
symptoms, causes, treatment, and prevention of the more common 
ailments of domestic animals, the composition and care of milk 
and the testing of milk for butter fat, a study of the more com- 
mon insect pests and plant diseases with the proper treatment for 
each, and the preparation of the different insecticides and fungi- 



PREFACE ix 

cides, — such topics as these might be selected as material for 
the work of a second course. 

The plan of work suggested in this Manual includes recitations 
following the reading and discussion of the portions of texts and 
bulletins treating each topic as it is taken up combined with exer- 
cises in the laboratory and supplemented wherever possible with 
pot-culture work and field experiments. 

Many of the laboratory exercises are the same that are used 
in the courses in agricultural colleges, for it is believed that the 
work in high school agriculture should hold the same relation to 
college agriculture as exists in the case of the other high school 
sciences, — botany, zoology, physics, chemistry, and in mathe- 
matics and languages, — with the expectation that many high 
schools will be able to do work in agriculture for which college 
credits can be allowed. 

In Part I, Exercise 1 is borrowed from Soil Physics Laboratory 
Guide by Professors Stevenson and Schaub of Iowa State College. 
Exercises 2 to 20 inclusive are taken from Laboratory Manvxd 
for Soil Physics by Professor J. G. Mosier of the University of 
Illinois. In a few instances they have been shghtly altered to 
adapt them to the purposes of the book. 

In Part II, page 52, acknowledgment is made to Dr. C. G. 
Hopkins and Professor J. H. Pettit of the University of Illinois 
for material used. 

In the work with corn the author has drawn very freely from 
the admirable circular. Studies of Corn and Its Uses, prepared by 
Professor Fred H. Rankin of the University of Illinois. 



CONTENTS 

PART I. STUDIES ABOUT SOILS 

PAGE 

I. Physical Composition of the Soil ... 1 
Exercise 1. Examination of Soil Particles with 
Microscope ....... 2 

II. Moisture Relations of Soils .... 3 

Exercise 2. Determination of Total Moisture in 
Samples of Field Soils ..... 4 

II. Different Forms of Soil Moisture ... 6 
Exercise 3. Determination of Capillary Moisture 

in Field Soils 8 

T. Soil Temperature and its Control . . .9 
Exercise 4. Effect of Drainage on Soil Tempera- 
ture 10 

V. Influence and Control of Color of Soils . 10 

Exercise 5. Effect of Color of Soil on Temperature 1 1 

71. Effect of Lime on Heavy Soils . . .12 

Exercise 6. Determination of the Effects of Lime 

on Plastic Soils . . . . . .13 

Exercise 7. Weight of Soils . . . .14 

Exercise 8. Determination of the Apparent Spe- 
cific Gravity of Surface Soil under Field Condi- 
tions 15 

Exercise 9. Determination of the Weight of Soil 
per Acre-foot . . . . . . .15 

Exercise 10. Determination of Specific Gravity of 
Soils. Volumetric Method .... 16 



xii CONTENTS 

VII. Questions concerning the Weight of Soils 

VIII. Porosity of Soils 

Exercise 11. Determination of Porosity — First 
Method 

IX. The Organic Matter in Soils 

Exercise 12. Determination by Ignition of the 
Loss of Organic Matter by Cropping 

X. The Water-retaining Power of Soils . 
Exercise 13. Power of Soils to retain Water 

XI. Effect of Compacting the Soil 

Exercise 14. Power of Compact Soils to retain 
Water 



XII. How Organic Matter in Soils affects their 
Water-holding Power 
Exercise 15. Effect of Organic Matter on Reten 
tion of Water ..... 

XIII. Capillary Movement of Soil Moisture 

Exercise 16. A Study of the Capillary Action of 
Soils 

XIV. A Common Mistake in Applying Manure 

Exercise 17. Effect of Organic Matter on Rise of 
Water in Soils 

XV. The Farmer's Control of Soil Moisture 

Exercise 18. Effect of Soil Mulches on Evapora 
tion of Water from Soils 

XVI. Mulches of Various Materials 

Exercise 19. Effect of Artificial Mulches upon 
Evaporation of Water from Soils . 



CONTENTS XIU 



PAGE 



XVII. Impeovement of Heavy Soils by Use of Farm 

Manure 35 

Exercise 20. The Effect of Organic Matter on 
Baking of Clay Soils 37 

PART II. STUDIES ABOUT CROPS 

XVIII. What Foods Plants Use and how they are 

Obtained 39 

Exercise 21. To show that Certain Plant 
Foods are Essential Preparation of Pot Cul- 
tures 44 

XIX. Farming in Four-gallon Pots . . .46 
Exercise 22. Applications of Plant for Crop 

Production 49 

XX. Experiment Field Work for High Schools 50 
Exercise 23. Plot-culture Tests to determine 

Plant Food Requirements of the Soil . . 52 
XXI. Questions relating to the Seeding of Crops 55 
Exercise 24. Crop Production: Oats. To 
determine what Amount of Seed per Acre 
gives Best Results . . . . .56 

XXII. Methods of Sowing Grains . . . .57 

Exercise 25. Test of Drilling versus Broad- 
casting ....... 58 

Exercise 26. Treating Seed Oats for Smut . 60 
Special Treatment of Seed ... 58 

Studies with Corn 62 

Exercise 27. Crop Production : Com. To 
determine how Close to plant Corn . . 63 



XIV 



CONTENTS 



XXV. 



XXVI. 



XXVII. 



XXVIII. 



XXIX. 



Problems in Cultivating Corn . 
Exercise 28. To show Effects of Different 
Methods of TiUage 

How Moisture may be saved for the Corn 

Crop 

Exercise 29. Determination of the Water 
Content of the Soil for Each Plot for Exer- 
cise 28 



of 



Growth of Corn Roots 
Exercise 30. A Study of Corn Roots . 
Exercise 31. Com Breeding: Selection 

Seed 

Exercise 32. Practice in Detasseling . 
Exercise 33. Experiment in Hand Pollination 

Observation Studies in the Cornfield 

Exercise 34. Field Work with Corn . 
Exercise 35. Studies of an Ear of Com 

Judging and Scoring Corn ' . 

Corn Score Card 

Exercise 36. Testing Corn for Seed 



FAGB 

64 
65 

66 



67 

67 
69 

71 
73 

74 

75 

76 
78 

82 
83 
88 



MANUAL OF AGRICULTURE 



PART I. — STUDIES ABOUT SOILS 
I. — Physical Composition of the Soil 

" The soil is not a mere inert mixture. Its parts 
have shape and size and arrangement, as well as being 
merely composed of certain substances. All of these 
parts have been separately formed, moved, and assorted, 
and then laid down together as we find them ; and, 
moreover, they are not even yet at rest, but are always 
taking new forms and new places and making new 
partnerships, entailing a never-ending series of myster- 
ies. From the soil all things come ; and into it all 
things at last return ; and yet it is always new and 
fresh and clean, and always ready for new generations. 
This soft, thin crust of the earth — so infinitesimally 
thin that it cannot be shown in proper scale on any 
globe or chart — supports all of the countless myriads 
of men and animals and plants, and has supported them 
for countless cycles, and will continue to yet support 
for other countless cycles. In view of all this achieve- 
ment, it is not strange that we do not yet know the soil 
and understand it ; and we are in mood to be patient 

1 



2 MANUAL OF AGRICULTURE 

with our shortcomings." — Bailey, Cyclopedia of 
American Agriculture. 

The soil, in an agricultural sense, is always a mixture 
of inorganic and organic matter. If either of these 
materials be lacking, it is not a true soil. The organic 
matter is composed of bits of decaying plant or animal 
substances — usually both. Disintegrated and pulver- 
ized rock constitute the inorganic portion of the soil. 
Soil particles differ in size, form, and arrangement, in 
weight and color. In most cultivated soils the in- 
organic material forms from 85 per cent to 95 per cent 
by weight of the mass. A sandy soil is usually defi- 
cient in organic matter, while peaty soils contain an 
excess of it. 

The object of Exercise 1 is to help the student to get 
a correct conception of the physical composition of some 
of the common types of soil. 

References : King, Tlie Soil, pp. 27-76. Fletcher, Soils, pp. 3- 
27, 46-74. Snyder, Soils and Fertilizers, pp. 9-56. Warington, 
Physical Properties of Soil, pp. 1-50. 

Exercise 1 

Examination of Soil Particles with Microscope 

I. — Place upon a glass slide a few grains of coarse sand and 
examine carefully with the low power of the microscope, noting 
these points : — 

(a) Color — white, gray, brown, red, or black. 

(6) Shape — angular, rounded, or irregular. 

(c) Simple or compound grains. 

(d) Size — coarse, medium, or fine. 



STUDIES ABOUT SOILS 3 

II. — In the same way study other types of soils — fine sand, 
loam, silt, clay, loess, and peat. 

On separate sheets make drawings of a number of particles of 
each kind of soil, and describe them with reference to (a), (6), (c), 
and (d). 

II. — Moisture Relations of Soils 

The study of the moisture relations of soils as af- 
fected by differences in their physical constitution, or 
by differences in their texture due to the character of 
the cultivation which they have received, is probably 
the largest and most interesting problem in soil physics. 

The capacity of a soil to absorb water in large 
amounts, to hold it in a form that does not prevent the 
free development of the roots of plants to a sufficient 
depth, and the ability to lift this water from below, as 
the needs of the growing crops demand it, up into the 
zone occupied by their roots, are the ideal conditions of 
the soil which the skillful farmer tries to secure. The 
study of soil physics is to help him understand the 
principles which control these conditions. 

In Exercise 2 the objects are: — 

(1) To show that the moisture content of a soil de- 
pends in part upon its surface conditions, i.e. what 
demands the crop growing on it is making for water, 
and what the character is of the surface cultivation. 

(2) To determine the relative amounts of water 
stored in the ground at different depths, — in strata 
commonly designated as surface, subsurface, and sub- 
soil. 



4 MANUAL OF AGRICULTURE 

The determination of the moisture content of a soil 
is a very simple process, and its frequent use on the 
farm would pay for the trouble it costs. In this way 
one may easily test the difference in the amounts of 
water in the ground at different depths due to fall 
versus spring plowing, to early versus late spring plow- 
ing, to differences resulting from various kinds of sur- 
face cultivation and surface mulching, etc. 

All of the w^ork should be done carefully and accu- 
rately in every exercise. Otherwise it has absolutely 
no value in results obtained and, besides, is very bad 
training. 

Keferences : King, The Soil., pp. 154-170. Fletcher, Soils^ pp. 75- 
84. Snyder, Soils and Fertilizers, pp. 22-25. Warington, Physical 
Properties of Soil, pp. 51-57, 64-73. 



Exercise 2 
Determination of Total Moisture in Samples of Field Soils 

According to directions given below, ^ collect samples of soils from 
(1) an old sod, (2) between the rows of corn, (3) tiUed ground 
where no crop is growing. Take the samples in each case from 
the surface, subsurface, and subsoil. 

1 Directions for collecting soil samples : For this purpose a one-and 
a-half or two-inch auger, with an extension making it 40 inches long, is 
used. In collecting samples for moisture determinations, expose the soil 
as little as possible to the air before putting in jars. Collect the surface 
soil to the depth of the plow Une, usually about 7 inches. After this 
part of the sample is removed, the hole is enlarged sufficiently so that 
the subsurface soil may be taken without coming in contact with the 
surface soil. Take the subsurface sample to the subsoil line as indi- 



STUDIES ABOUT SOILS 



Mark and carefully weigh six soil pans. Run all experiments 
in duplicates for the sake of greater accuracy. 

Place in each soil pan 100 grains of the soil sample to be 
studied, taking the weights rapidly to prevent loss by evaporation. 
Put them in the drying oven for five hours at a temperature of 
100° to 110° 0. Cool to room temperature and weigh at once. 
The loss in weight represents the total moisture content of the 
soil. 

If three students work together, one might take the surface, an- 
other the subsurface, and the third the subsoil. Then compare 
results. 

Tabulate the results as follows : — 



Total Moisture Determination 



Kind of 

Soil. 



Pan 

No. 



Wt. of 
Pan. 



Wt. of 
Soil. 



Wt. of 
Soil and Pan, 



Wt. of Dry 
Soil and Pan. 



Wt. of 
Dry Soil. 



Loss 
of Wt 



Per Cent 
Moisture. 



cated by the change in color, texture, and physical composition. Com- 
monly this line is found at a depth of 16 to 20 inches. Enlarge 
and clean out the hole as before. Since the change from subsurface 
to subsoil is not a sharp line, but usually somewhat gradual, we dis- 
card about two inches of the intermeaiate mixture. The subsoil is then 
collected to a depth of 40 inches, if possible. 

In some soils the subsurface layer may be absent, the subsoil being 
reached by the plow, while in others, as in peaty and sandy soils, no 
true subsoil may be found within 40 inches of the surface. In such 
cases only two samples are taken. 



6 MANUAL OF AGRICULTURE 

State the weather conditions when the samples were collected 
and the amount of the rainfall during the previous week. 

Which soil had largest water content ? Which had the least ? 
What is the explanation ? Was most water found in the surface, 
subsurface, or subsoil ? 

III. — Different Forms of Soil Moisture 

Most of the water in the soil comes from the rains 
and snows that fall on the surface of the ground. A 
part of what falls is quickly evaporated before it soaks 
into the ground. Another portion forms into rills and 
flows over the surface joining larger streams and usually 
carrying in its currents more or less of the richest par- 
ticles of the soil, to be eventually lost in the sea. The 
amount of water, with its burden of soil, that is thus 
lost to the farmer depends largely upon the topography 
of the land and the condition of its surface. In a hilly 
country, and wherever the upper soil is packed and 
bare of vegetation, the surface wash is likely to be 
serious. 

The remaining part of the rainfall and melting snows 
gradually sinks into the ground, and is either absorbed 
by the soil particles and held as a film over their sur- 
faces, or it percolates down through the cracks and 
crevices in the soil, obeying the law of gravity, until 
it reaches the level of standing water, commonly spoken 
of as the water table. 

Of all these divisions of the water which comes to the 
earth as rain and snow, it is only the portion that soaks 
into the ground and is held as film water around the 



STUDIES ABOUT SOILS 7 

soil particles which is directly concerned in supplying 
growing plants with moisture, and for this reason is of 
greatest interest to the agriculturist. This moisture 
is called capillary moisture because it moves in all direc- 
tions through the interstices between the soil particles 
by the force of capillary attraction, just as oil in a lamp 
flows upward through the wick. 

But not all of the film water about the soil grains is 
free to move under the influence of capillary attraction. 
Adhering to the surfaces of all solids of atmospheric 
temperature is an exceedingly thin film of moisture 
which can be expelled only by exposure to a high de- 
gree of heat. This film of water is known as hygro- 
scopic moisture^ and can be driven off from the soils only 
by keeping them in a drying oven at a temperature of 
about 105° C. for five or six hours. Roots of plants are 
unable to overcome the adhesive power which holds 
this film of moisture to the soil particles. On the 
other hand, the greater part of the layer of moisture 
surrounding the soil grains is held so loosely that the 
plant roots can absorb it readily by a force called osmo- 
sis^ and when exposed to the air it is carried off by 
evaporation. 

In Exercise 2 the total moisture content of the soil 
was determined by using the drying oven and expelling 
both the capillary and the hygroscopic moisture at the 
same time. The residue remaining in the soil pans is 
water-free soil, and this is taken as the basis in all com- 
putations and data relating to soils, because it is the 
only uniform condition that can be secured. 



8 MANUAL OF AGRICULTURE 

In Exercise 3 only a determination of the capillary 
moisture is sought, and this requires merely an exposure 
of the soils to the air until a constant weight is reached, 
that is, until all the capillary moisture has evaporated. 

Eeferences : King, The Soil, pp. 173-178. Fletcher, Soils, pp. 
29-31, 87-90. Warington, Physical Properties of Soil, pp. 92-107. 

Exercise 3 

Determination of Capillary Moisture in Field Soils 

Use soils from the same samples taken for Exercise 2. (The 
jars should be kept tightly sealed except when the samples are 
being weighed out. Mix the soils well by thoroughly shaking the 
jars before opening.) 

Number and weigh carefully 6 soil pans. Place in each 100 
grams of soil, running duplicates of surface, subsurface, and sub- 
soil. With a glass rod carefully break up all lumps and spread the 
soil evenly over bottom of pan. Let the soils dry at room tem- 
perature, and take the weights every 24 hours. When the weight 
becomes constant, the loss indicates the amount of capillary mois- 
ture. 

Compute the percentage of capillary moisture in each sample on 
the basis of the water-free soil as found in Exercise 2. Tabulate 
the results as in the previous exercise. 

Notice that the difference between the total moisture content and 
the amount of capillary moisture in a sample represents approxi- 
mately the hygroscopic moisture of that soil. 

How does this compare in amount with the per cent of capillary 
moisture ? 

Are the amounts about the same for all of the soils and in the 
same relative order for surface, subsurface, and subsoil ? 



STUDIES ABOUT SOILS 9 

IV. — Soil Temperature and its Control 

A warm soil is superior to one that is cold for crop 
production. For each kind of crop there is a minimum 
temperature below which its seeds will not germinate. 
There is also for every kind of plant an optimum tem- 
perature for growth. A plant produced from a seed 
that has germinated in a soil too cold for the plant to 
start with a vigorous growth becomes stunted and never 
reaches maximum development. The various forms of 
microorganisms and chemical processes in the soil, upon 
whose activities the fertility of soils is largely depend- 
ent, require a warm environment for their best work. 

The gain of a few days at the beginning of the sea- 
son, for many crops, constitutes a large factor in their 
success. 

Most farmers do not realize that soil temperature is 
a thing over which they may have much control, and 
probably a majority of them would think that the dif- 
ference of a few degrees is of too little consequence to be 
considered. But the scientist, the engineer, the pro- 
fessional man, the manufacturer, and the business man 
have all been trained to appreciate the importance of 
every factor that enters into their work. It is here 
that the training of the farmer has been especially 
weak; and it is the province of the study of the science 
of agriculture to correct this fault in his training and 
teach him how he may control conditions which before 
he had supposed were beyond his power to influence. 

An undrained or wet soil is cooler than a dry one, 



10 MANUAL OF AGRICULTURE 

because there is so much greater evaporation of mois- 
ture from its surface, and the amount of heat required 
to vaporize a pound of water is very considerable. It 
requires foQr or five times as many heat units to raise 
a given weight of water 1° F. as are needed for the 
same amount of dry soil. The object in Exercise 4 is 
to demonstrate and impress these facts. 

Keferences : King, The Soil, pp. 218-227, 234-238. Fletcher, 
Soils, pp. 33-34. Warington, Physical Properties of Soil, pp. 165-178. 

Exercise 4 

Effect of Drainage on Soil Temperature 

Make two wooden boxes 3x4 feet and 6 inches deep, building 
one water-tight and the other loose enough to allow the water to 
drain off. Fill each box with the same kind of soil, and apply the 
same amounts of water till drainage begins in the loose box. The 
boxes should stand in the open air, where evaporation is free. After 
drainage has ceased, take the temperature of the soils in each box 
hourly, on a clear day, at the depths of 1, 2, and 4 inches. 

Give explanations for the differences in temperature. 

Why is clay called a cold soil, and sand warm 1 

V. — Influence and Control of Color of Soils 

The color of the surface soil has a marked influence 
on its temperature. Between soils of dark color and 
those of a light hue there is often found a difference of 
5° to 10° F. at a depth of 2 to 5 inches. For many crops 
early in the season this is a matter of considerable im- 
portance. Soils containing large amounts of organic 



STUDIES ABOUT SOILS 11 

matter are dark colored. Through careless or unwise 
cultivation, soils gradually grow lighter colored. The 
farmer's control of these conditions comes mainly- 
through the use of barnyard manure and the plowing 
under of green crops. In Exercise 5 there is an op- 
portunity to demonstrate two things : — 

(1) Dark-colored soils absorb a larger proportion of 
heat from the rays of the sun than do light-colored soils. 

(2) Seeds will germinate more quickly and plants 
grow more rapidly in soils of dark color than in those 
of light color. 

References : King, The Soil, p. 230. Fletcher, Soils, pp. 34-36. 
Warington, Physical Properties of Soil, pp. 161-164. 

Exercise 5 
Effect of Color of Soil on Temperature 

Fill a wooden tray 6 feet long, 3 feet wide, and 6 inches 
deep with well-pulverized soil of a light color. By a wire drawn 
taut across the tray lengthwise, divide the surface into halves. 
Then, by other lines drawn crosswise of the tray, divide each half 
into 6 equal plots. Designate the corresponding plots in each half 
by the same letter, and in each two plots, similarly marked, plant 
the same kind and number of seeds, using com, peas, beans, oats, 
wheat, and rye. In one half of the tray bury the seeds f inch 
deep in the soil ; in the other half cover them with i inch of the 
light-colored earth, ^ and then add \ inch of some dark soil or of 
soot, so that the seeds in every plot are covered to the same depth. 

1 If it is not easy to obtain a soil that is quite light or quite dark in 
color, the soil in half of the tray can be whitened by a thin dressing of 
lime or chalk dust, and the other half darkened by soot. 



12 MANUAL OF AGRICULTURE 

(a) Every morning and evening observe the number of plants 
showing above the surface on each plot and carefully record them, 
comparing results in the light-colored soil with those in the dark 
earth. 

(b) Choose a clear day and make observations of the tempera- 
tures of the soils in the two halves of the tray. Insert thermome- 
ters in the soil to the depths of 1, 2, and 4 inches in both 
the light-colored earth and the dark-colored earth, and take hourly 
readings from 7 a.m. to 5 p.m. Keep all parts of the tray equally 
moist. 

Each student may look after the planting of a single plot, but 
he must make observations on all plots in the tray and hand them 
in in tabular form. 

Which tray shows the higher temperature ? Why ? 

Why can you see the corn rows on the low, black land sooner 
after planting than upon the higher, light-colored soil ? 

VI. — Effect of Lime on Heavy Soils 

One of the most difficult problems that many farmers 
have to deal with in the cultivation of their land is how 
to handle their clay soils and fine silts so that the 
proper texture of the soil shall be preserved. 

A peculiarity of these soils if they are stirred when 
too moist, is that they become pasty and run together so 
that on drying they are hard like cement. This quality 
is due to the fineness of the soil grains, which are so 
small that if they are packed closely together the in- 
terstices between them are not large enough for either 
water or air to penetrate. When a soil is in this con- 
dition, it is of little value for farming purposes. A soil 



STUDIES ABOUT SOILS 13 

is said to be in good tilth when the individual soil 
grains are massed together in crumbs or granules about 
the size of timothy seed. Now it has been discovered 
that the action of lime upon a clay soil is to cause the 
fine particles to flocculate and assume a crumbly tex- 
ture, making the soil lighter to till and more easily 
drained. 

The object in Exercise 6 is to demonstrate to the 
student the possibility of controlling the conditions of 
texture in fine-grained soils by the application of lime. 

References : King, The Soil, p. 30. Warington, Physical Prop- 
erties of Soils, pp. 30-33. 

Exercise 6 

Determination of the Effects of Lime on Plastic Soils 

Two students may work together in this experiment. 

Weigh out six 300-gram samples of the clay soil, using them 
as follows : to sample 

No. 1, check, add no lime. 

No. 2, add .5 gram of air-slacked lime. 

No. 3, add 1 gram of air-slacked lime. 

No. 4, add 5 grams of air-slacked lime. 

No. 5, add 10 grams of air-slacked lime. 

No. 6, add 10 grams sand. 

Mix each sample thoroughly in a soil pan with the lime, and add 
just enough water to make plastic. 

Fill the semicircular molds,^ first placing in each a damp, thin 

1 It may be easier to make molds with dimensions 4" x 2" x 1". 

The test can be made by suspending from the middle of the stick a 
bucket into which sand is slowly poured until the weight is secured 
which is necessary to break the stick. 



14 MANUAL OF AGRICULTURE 

cloth to facilitate the removal of the clay. Make duplicates of each 
sample, beiDg careful to compress each to the same degree. Place 
on a cloth in a soil pan and dry in an oven for five hours at 105° C. 

Test the strength of each brick by supporting the ends so as to 
allow just three inches between points of support. Hang a weight 
pan in middle of the brick, and determine the weight necessary to 
break each one. 

Express data in tabular form. 

Explain the effect of lime. 

Why does the sand not have as much effect as the lime on the 
breaking strength ? 

Exercise 7 

Weight of Soils 

Determine the cubic contents of a box the three dimensions of 
which are from 6 to 1 2 inches. Take the weight of the box and 
contents when filled with different air-dry soils, viz. sand, clay, 
loam, loess, and peaty soil. In filling the box, do not compact the 
soil. From the data obtained, compute the weight per cubic foot 
of each soil. 

Calculate the weight of an acre of each soil to the usual depth 
of the plow line, 7 inches. 

The weight of a cubic foot of water is 62.42 pounds. The ap- 
parent specific gravity of each soil tested may be found as follows : — 

Volume wt. of soil . .^ -. ^ n 

-— = apparent specinc gravity of soil. 

Volume wt. of water 

In this computation the water free weight of the soil should be 
used. To do this, determine the per cent of hygroscopic moisture 
in a small sample of this soil. The weight of any given volume 
of this soil divided by one plus the rate per cent of the moisture, 
will give as a quotient the weight of water-free soil. 



STUDIES ABOUT SOILS 15 

Exercise 8 

Determination of the Apparent Specific Gravity of Surface 
Soil under Field Conditions 

Take a tube provided for the purpose, and force it into the 
ground to the depth of six inches. Kemove soil to a weighed pan, 
and dry in the oven at 105° C. for at least ten hours. Find weight 
of volume of water equal to that of the soil taken, and divide the 
weight of the water-free soil by this. The result wiU be the ap- 
parent specific gravity. 

The apparent specific gravity of soils in the field may be taken 
as an approximate indication of the tilth of the soils, since the 
better the tilth the less will be the apparent specific gravity for 
the same kind of soil. This is due to the fact that soils in good 
tilth are looser on account of the presence of organic matter and 
better granulation. The apparent specific gravity of a continu- 
ously cropped soil is higher than one having proper rotations. 
Why? 

What would be the approximate weight of a cubic foot of soil 
under the above conditions ? 



Exercise 9 

Determination of the Weight of Soil per Acre foot 

Drive into the soil a brass tube (8" long and about 3" in diam- 
eter, sharpened at its lower edge) until the top is level with the 
surface. 

Dig away the soil around the tube ; empty the tube upon a 
piece of oilcloth and transfer the soil to a Mason jar ; carefully drive 
the tube down again, and thus obtain a sample of the succeeding 



16 MANUAL OF AGRICULTURE 

eight inches. Repeat this operation until eight-inch samples of 
the soil have been secured to any desired depth. Carefully weigh 
each sample. Determine the total moisture in 100 grams of soil 
from each depth, and from these data determine the weight of the 
water-free soil. Calculate in cubic inches the content of the tube. 
Calculate the weight of an acre of soil to the depth at which 
each sample was taken. Tabulate the results. 



Exercise 10 

Determination of Specific Gravity of Soils. Volumetric 
Method 

Determine exactly the amount of water required to fill the 
measuring flask to the 50 cubic centimeter mark by using a 
burette. Place about 20 grams of soil in the flask and add a 
measured quantity of distilled water, and shake well to expel the 
air from the soil. 

Fill the flask up to the mark from the burette, and note the 
total amount of water used, including the hygroscopic water of the 
soil. This amount, subtracted from the volume of the flask, will 
give the water displaced by the soil. Calculate the specific gravity 
and tabulate the results. 

Use for this experiment sand, clay, and loam soils. 

VII. — Questions concerning the Weight of Soils 

If the soil were a solid mass, the determination of its 
weight would be a simple matter. The specific gravity 
of the material which forms the great bulk of most soils 
is about 2.6. Since a cubic foot of water weighs 
nearly 62^^ pounds, a cubic foot of soil, then, would 



STUDIES ABOUT SOILS 17 

weigh 2.6 times 621^ pounds, or 162| pounds. (This, of 
course, refers to the weight of water-free soil.) 

But the fact is, a soil is not a solid mass. On the 
contrary, it is composed of more or less spherical par- 
ticles which touch each other only at certain points 
of contact. Nearly 50 per cent of a given volume of 
cultivated soil is air space. This pore space necessa- 
rily reduces the weight of any volume of soil much 
below the specific gravity of its constituents ; hence, 
we use the two terms, " real specific gravity " and " ap- 
parent specific gravity." 

There is a wide variation in the weights of different 
arable soils, owing to the differences in the amounts of 
humus in their composition, and in the size of their soil 
particles. For these reasons surface soils are usually 
lighter than subsoils. A fertile garden soil weighs 
about 70 pounds per cubic foot, while an ordinary sandy 
loam weighs 90 to 95 pounds. 

The figures taken for the approximate weight of dry 
soil on an acre of arable land are 4,000,000 pounds to 
the depth of 12 inches, and 2,000,000 pounds for the 
7 surface inches. 

Exercises 7, 8, 9, and 10 are given that the student 
may have opportunity to verify the statements made 
by different writers in regard to the weights and 
specific gravities of soils, and also that he may learn at 
first hand how soils of different types compare in these 
respects. 

References : Fletcher, Soils, pp. 26-27. Snyder, Soils and Fertil- 
izers, pp. 9-11. Warington, Physical Properties of Soil, pp. 41-49. 



18 MANUAL OF AGRICULTUUE 

VIII. —Porosity of Soils 

As has been stated in a former paragraph, because 
the soil mass is made up of rounded particles more or 
less loosely packed together, there is left between them 
a considerable space that is occupied by air or water, 
and is called the 'pore space of the soil. The amount 
of pore space varies from something over 50 per cent in 
very ^yiq clay soils to 25 or 30 per cent in coarse sands 
of uniform texture. It is greatest in the fine-grained 
soils because these particles, unlike those of sandy soils, 
are too light to pack closely of their own weight. 

Under ordinary field conditions of a cultivated soil, 
the pore space is increased by the stirring of the ground 
and the addition of organic matter. It is the pore 
space of a soil which measures its capacity to hold 
water. For example, if 50 per cent of the surface foot 
of a certain soil is pore space, the capacity of that soil 
to take up water before it is forced to flow away over 
the surface or to penetrate deeper into the ground is 
equal to six inches of rainfall. 

Moreover, the various forms of living organisms that 
work in the soil and are essential to its fertility require 
the presence of air to live and work. Both the oxygen 
and the nitrogen in the air are needed for the chemical 
combinations that take place in a fertile soil. The 
roots of growing plants demand air just as animals do, 
and when the supply is shut off the plants die. 

For all these reasons a fertile soil must have a gen- 
erous amount of pore space for the circulation of air. 



STUDIES ABOUT SOILS 19 

These are important matters in the business of grow- 
ing crops, and the farmer should thoroughly understand 
and appreciate them. 

Exercise 11 presents two methods for determining 
the amount of pore space in soils. 

Reference : Warington, Physical Properties of Soil, pp. 64-73. 

Exercise 11 

Determination of Porosity 
FiKST Method 

Weigh a graduated cylinder. 

Use sand, loam, silt, clay, and peat. 

Fill to the 50 or 100 cubic centimeter mark with soil not 
compacted, and weigh. Compute the amount of water-free soil in 
this. 

( Volume of soil X real specific gravity) — wt. of water-free soil 
Volume of soil x real specific gravity 

= per cent of pore space. 

What effect does size of particles have on total amount of pore 
space ? 

Does the amount of pore space increase or decrease with the 
amount of organic matter ? 

Which of the soils have the largest pores ? Does this mean the 
greatest amount of pore space ? 

Second Method 

Find what per cent the apparent specific gravity is of the real 
specific gravity, and subtract this from 100 per cent. The re- 
mainder expresses the per cent of pore space in the soil. 



20 MANUAL OF AGRICULTURE 

Why does the porosity of soils vary as the apparent specific 
gravity ? 

IX. — The Organic Matter in Soils 

The common sources of the organic matter in soils 
are plants and animals whose bodies, after life leaves 
them, fall to the ground and are gradually disintegrated 
and mingled with the finely ground portions of the 
earth's crust. Here, through the action of soil bacteria, 
the particles are decomposed into the elements from 
which they were originally formed, and thus their cycle 
of existence is completed. 

In the intermediate stages of decomposition this 
organic matter in the soil is called humus, and is a most 
important factor in the matter of the soil's producing 
power. 

Humus is the chief source of soil nitrogen. Its pres- 
ence in the soil usually imparts to it the dark color 
which is regarded as one of the surest indications of 
a fertile soil. Many of the most important physical 
properties essential to the permanent productiveness of 
soils are dependent upon the presence of a certain pro- 
portion of organic matter mixed with the rock particles. 

In Exercise 12 the student is given a method of de- 
termining with some degree of accuracy the per cent of 
organic matter in any given sample of soil. Ignition 
is not regarded as an altogether satisfactory means of 
taking this measure, because the heat that consumes 
the organic matter also drives off any volatile salts and 
water of hydration present, thus indicating by the loss 



STUDIES ABOUT SOILS 21 

of weight in the ignited soil a greater amount of or- 
ganic matter than the soil may have contained. This 
is especially true in the case of clay subsoils. However, 
with most surface soils the results are approximately 
correct and are of value in making comparisons between 
different soils. 

References : King, The Soil, pp. 94-95. Fletcher, Soils, pp. 53, 
• 72, 322-333. Snyder, Soils and Fertilizers, pp. 86-96. 



Exercise 12 

Determination by Ignition of the Loss of Organic Matter by 
Cropping 

It is a recognized fact that constant cropping with grain tends 
to diminish rapidly the amount of organic matter in the soil unless 
great care is taken to maintain the supply by the use of green 
manure crops or the application of farmyard manure. This loss 
changes the physical character of the soil. The result is to destroy 
granulation, lessen the water-holding capacity of the soil, lower 
the temperature, and interfere with proper aeration. 

Get one sample of the surface soil from a field that has been 
cropped heavily for years, and another sample from the sod border 
as near as possible to this field, and determine the loss in weight of 
each soil on ignition, which will give an indication of the organic 
matter content. 

Weigh out 5 grams of water-free soil, or air-dry soil calculated 
to a water-free basis, and ignite in a small crucible to low red heat 
for 15 to 20 minutes. Cool in a desiccator and weigh. 

Tabulate your results. 

Which of the soils loses more ? Why 1 



22 MANUAL OF AGRICULTURE 

X. — The Water-retaining Power of Soils 

The capacity of a soil to absorb or hold water is 
limited by the amount of its total pore space, which, as 
is shown in previous paragraphs, varies according to the 
composition and texture of the soil from about 25 per 
cent to more than 50 per cent. This means tliat a satu- 
rated soil may contain from 436 tons to 697 tons of 
water in the upper foot of soil on an acre. 

However, a productive soil is never saturated with 
water except possibly for a short time immediately 
after a long and heavy rainfall. Soils in which water 
stands for any length of time filling the pore spaces are 
boggy and unproductive, and the water-table must be 
lowered by artificial drainage before the lands can be 
valuable for farming purposes. 

But it is the power of drained soils to retain moisture, 
which is of real interest to the farmer, for this is the 
water supply on which the growing crops must depend. 

It has been stated in a former paragraph that the 
moisture which is retained in a soil is held there in the 
form of a film around each soil particle, and is known 
as capillary moisture. Hence, it is readily seen that 
the soil which possesses in any given volume the great- 
est surface area in the grains which compose it has the 
greatest water-retaining capacity. For this reason the 
finest-grained soils have the greatest power to retain 
moisture. This is illustrated as follows: In a cubical 
box measuring 12 inches, only one ball having a diame- 
ter of 12 inches can be placed. The surface of this 



STUDIES ABOUT SOILS 23 

ball, by the formula for finding the surface of a sphere 
(^S = TT I> 2), equals 144 ir inches. If balls of half this 
diameter be placed in the box, it will contain eight of 
them, and their combined surfaces (/S'=7r x6x6x8) 
are 288 tt inches. That is, by reducing the diameters of 
the spheres by one half, the aggregate area of their sur- 
faces is doubled. 

While the soil particles composing any soil are not 
perfect spheres and are not of uniform size, it still holds 
that the finer the grains and the greater the number of 
them in a given volume of soil the greater will be the 
internal surface of the soil and the greater its water- 
retaining power. 

Exercise 13, therefore, is a practical demonstration 
of the differences in the capacities of soils to retain 
moisture largely in accordance with the relative sizes of 
their soil particles. 

References : King, The Soil, pp. 157-162. Fletcher, Soils, 
pp. 80-82. Waringtou, Physical Properties of Soil, pp. 74-85. 

Exercise 13 

Power of Soils to retain Water 

Fill tubes having perforated bottoms with sand, sUt, loam, and 
clay. 

Before filling, place disks of damp cheese cloth in the bottoms of 
the tubes and then weigh them. Fill the tubes up to the crease, 
one inch from the top, by pouring the soil in gently through a fun- 
nel, the tube being held vertically, and be careful not to compact the 
soil by jarring. Weigh the filled tubes and place in an empty gal- 



24 MANUAL OF AGRICULTURE 

vanized iron box. Pour water into the box till it is on the same 
level with the soil in the tubes, thus allowing the water to pass up 
through the soils. Note time required for soils to become moist on 
top. When the soils have become thoroughly saturated, remove 
the tubes and place them in a pan to drain. Weigh from day to 
day till drainage ceases. 

Determine the amount of water-free soil by finding total mois- 
ture content of the soil when used. 

Measure depth of the settled soils. 

Calculate the per cent of water retained, the weight per cubic 
foot of soil that this represents, using the apparent specific gravity 
and the acre inches of water. 

Express your results in tabular form. 

Land recently plowed six inches deep will absorb how many 
inches of rainfall without any run-off ? 

Is there any advantage in deep plowing on rolling land ? 

What is a saturated soil ? 

XI. — Effect of compacting the Soil 

There is some difference of opinion among farmers 
as to whether rolling or otherwise compacting the soil 
increases its capacity to retain moisture. It is fre- 
quently apparent that the soil on the surface of the 
ground where it has been packed by footprints has 
more moisture than the loose soil around it. It is true 
that, by pressing more closely together the grains of 
loose material on the surface and destroying the open 
spaces which were too large to exert capillary action, 
the movement of water from below towards the surface 
has been increased, and for a time there will be a gain 



STUDIES ABOUT SOILS 25 

in the amount of water in the upper layer of the soil, 
but at the expense of the layers below. In the case of 
some very light soils, where the particles in their com- 
position are quite uniformly coarse and the pore spaces 
large, compacting undoubtedly increases their water- 
retaining power. 

Exercise 14 is given for the purpose of comparing 
compact soils with loose soils to determine which has 
the greater capacity to retain water. 

References: King, The Soil, pp. 200-202. Fletcher, Soils, pp. 
171-177. 

Exercise 14 
Power of Compact Soils to retain Water 

Use the same tubes and soils as in Exercise 1 3, and run them at 
the same time if possible. When you have filled the tubes one- 
third full of soil, hold them vertically six inches above a solid table, 
and let them fall three times ; repeat this when two-thirds full, and 
again when full. Use great care to compact the soil in all the tubes 
alike. ^ 

Conduct the experiment precisely as in the previous exercise, 
except in compacting the soils. Calculate the per cent of water 
retained, the weight of water per cubic foot of soil, using the ap- 
parent specific gravity and the acre inches of water for each soil. 

Tabulate your results. 

1 In the soil-physics laboratories of agricultural colleges an appara- 
tus for compacting the soils uniformly is used. An iron plunger just 
fitting the soil tubes is attached to the end of a rod on which moves 
freely a weight of several pounds. The plunger is placed upon the soil 
in the tube and the weight dropped a given number of times from a 
mark on the rod. A strong wood frame is needed for the apparatus. 



26 MANUAL OF AGRICULTURE 

Which soil becomes wet on top first 1 Why 1 How does this 
coiTespoud with total pore space*? Which soil is drained first? 
Why ? How does this correspond with total pore space ? What 
effect does organic matter have on retention of water ? 

How does rolling affect the water-retaining capacity of a soil ? 

XII. — How Organic Matter in Soils affects their 
Water-holding Power 

The chief object sought in the study of the science 
of agriculture is to discover how the farmer may con- 
trol or modify to his advantage the conditions that 
affect the growing of crops. It is certain that crop 
yields are often seriously limited because the soil does 
not contain sufficient moisture to supply their needs. 

Exercise 15 is given that the student may test the 
effect of an increase in the amount of organic matter in 
the soil upon its water-retaining powers. 

References : King, The Soil, pp. 288-291. Snyder, Soils and 
Fertilizers, pp. 37-38. 

Exercise 15 

Effect of Organic Matter on Retention of Water 

Use same tubes as in preceding exercises, but compact in one, 
sand, and in the others, sand and peat in the following propor- 
tions : 190 grams of sand and 10 grams of peat thoroughly mixed ; 
175 grams of sand and 25 grams of peat ; and 150 grams of sand 
and 50 grams of peat.^ 

1 If peat cannot be obtained conveniently, thoroughly rotted dry 
manure may be used in its place. The manure should be made fine 
by rubbing before it is mixed with the sand. 



STUDIES ABOUT SOILS 27 

Treat as in the preceding, and determine the grams of water re- 
tained, also the per cent of water retained, based upon the total 
amount of sand and peat used in each tube. 

Tabulate results. 

What per cent of organic matter was in each tube 1 

How many grams of water did the 10 grams of organic matter 
retain ? The 25 grams ? The 50 grams ? 

XIII. — Capillary Movement of Soil Moisture 

As the films of moisture surrounding the soil grains 
which lie near the surface of the ground are removed 
by evaporation into the air, and others enfolding the 
particles of soil at greater depths are taken up by the 
tiny root hairs to supply the plants with water, there is 
a steady flow of moisture from below and from every 
side, if the soil is in a proper state of tilth, to take the 
place of that which has been withdrawn. This move- 
ment of moisture through the ground is made possible 
by the capillary action of soils, and in some soils its 
force is exerted through distances of many feet. If it 
were not for this capillary movement of moisture in 
soils, it would be utterly impossible in many regions to 
grow crops, since there is no rainfall there during the 
growing season. Indeed, there are few places where 
the rainfall is sufficient in quantity and distributed 
evenly enough during the months in which crops make 
their growth to meet their needs for moisture if none 
could be pumped up from the reservoirs below. 

This power of a soil to move w^ater through its mass 
is so largely dependent upon physical conditions which 



28 MANUAL OF AGRICULTURE 

cultivation can affect that it should be one of the sub- 
jects of greatest interest and study for the farmer. 

In Exercise 16 the students are able to observe the 
relative lifting powers of soils of different types and 
of soils of the same type but in different conditions of 
tilth. 

The value of such ocular demonstrations to a student 
of the processes which are constantly in operation in 
the soil under his feet, and which it is possible for him 
to control, in a large measure, to the advantage of his 
crops, if he understands the principles on which these 
processes work, makes exercises of this sort especially 
desirable. 

References: King, The Soil, pp. 135-142. Fletcher, Soils, pp. 
87-90, 95-96. Warington, Physical Properties of Soil, pp. 92-108. 



Exercise 16 
A Study of the Capillary Action of Soils 

The capillary power of soils is influenced by several factors, the 
most important of these being the physical composition, texture, 
and compactness of the soil. In field soils all these are changed 
by continuous cropping, and the capillary action is therefore al- 
tered. Of these factors, physical composition is most important, 
especially the amount of the diff'erent grades of the inorganic 
constituents. 

The soils selected are as follows : — 

1. Fine sand. 

2. Coarse sand. 

3. Loam. 



STUDIES ABOUT SOILS 29 

4. Clay. 

5. Sod from an old pasture. 

6. Heavily cropped soil as near the type of 5 as possible. 

Use glass tubes one inch in diameter and four or five feet in 
length. One end of the large glass tubes is closed by means of a 
piece of muslin firmly tied on. These tubes are then filled with 
the finely pulverized and sifted air-dried soils. Great care must 
be exercised in filling these tubes so as not to separate the coarse 
and fine particles. This may best be accomplished by holding 
the tube vertically during the process of filling. When the tubes 
are filled, the soil is compacted slightly by letting each tube drop 
four times a distance of four inches upon a book. The tubes are 
now placed in a supporting frame in such a manner that the ends 
shall dip one-half inch beneath the surface of the water contained 
in the tray.^ The experiment is now ready for observation, and the 
datum to be obtained at each reading is the total height to which 
the water has risen. The readings are to be taken as nearly as 
possible at the intervals stated below and tabulated. 

Observe height of moisture after ^ hour, 1 hour, 2 hours, 3 
hours, 6 hours, 9 hours, 12 hours, 24 hours, 36 hours, 48 hours; 
3, 4, 5, 6, 7, and 8 days. 

Make a close comparison of the different tubes. 

Which shows the most rapid rise 1 Why ? 

Plot the heights of the water of the different tubes at different 
times. 

At the end of one hour, which shows the greatest rise, clay or 
sand ? Which at the end of a week ? Why ? 

What effect does organic matter have, as shown in 5 and 6 ? 

What effect does size of particles have on rapidity of capillary 
movement, not taking height into account ? 

1 Arrange so that there shall be a continuous flow of water through 
the tray, keeping the depth half an inch above the bottoms of the tubes. 



30 MANUAL OF AGRICULTURE 

XIV. — A Common Mistake in applying Manure 

Exercise 17 differs from No. 16 only in providing for 
experiments to determine the effect on the capillary 
movement of water caused by the application of farm 
manures or the plowing under of green crops. 

The tests may easily be varied from time to time to 
cover a great many different conditions and to answer 
questions that may arise in the minds of the students 
as to what would be the results of certain practices. 

If the crop at any time during its growing season is 
forced to depend for its moisture upon the supply of 
water which is held in store at some distance below the 
surface, any material, like coarse manure or unrotted 
clover, which breaks the connection of capillary tubes 
in the soil between the stratum where the plant roots 
are growing and the one in which the water is held 
will prove to be a serious disadvantage to the crop. 

Experiments like the following are especially valuable, 
because they make clear to the student the reasons why 
certain ways of doing things on the farm frequently 
give bad results. 

Exercise 17 

Effect of Organic Matter on Rise of Water in Soils 

Class exercise in which each member of the class is to take 
daily observations on the height of the water in the tubes and 
note effect of organic matter on rise of water. 

After tying a cloth firmly over the ends of three two-inch glass 
tubes two feet long, fill them to the height of one foot with soil 



STUDIES ABOUT SOILS 31 

compacted by letting the tube drop four times on a book from 
height of four inches for every six inches of soil put into the tube. 

Use finely pulverized, air-dried loam, filling tube No. 1 with the 
soil alone. Fill tube No. 2 with one foot of soil, then add a two- 
inch layer of cut straw or sawdust, and fill to the top with soil. 
Fill the third tube in the same way, except that a one-inch layer 
of fine, well-rotted manure is used in place of the straw or sawdust. 

Place the tubes in a frame so that the lower ends shall stand in 
half an inch of water. Notice the rise of capillary water in each 
tube, and at the end of a week make a complete report of your 
observations. 

What is the efibct of plowing under large amounts of poorly 
rotted manure in the spring ? 

What advantage in this respect has fall plowing ? 

XV. — The Farmer's Control of Soil Moisture 

The control of the moisture relations of soils in- 
cludes : — 

1. Increasing the amount of water in the soil either 
by irrigation or by rendering the surface more loose and 
porous, so that it will absorb a larger proportion of the 
water that falls upon it in the shape of rain and melt- 
ing snows. 

2. Diminishing the amount of water in the soil either 
by conducting it away through surface ditches before 
it soaks into the ground, or by tile drains laid beneath 
the surface for the purpose of lowering the water- 
table. 

3. Increasing the water-holding capacity of the soil 
by cultivation and the application of organic matters. 



32 MANUAL OF AGRICULTURE 

4. Hastening or retarding the movements of water 
in the soil by different kinds of cultivation, or by the 
use of manures and green crops plowed under. 

5. Conserving the supply of water that has already 
been taken into the soil, and preventing its unnecessary 
loss by evaporation from the surface. 

All these questions except the last have been dis- 
cussed in previous exercises. In Exercise 18 the object 
is to discover the most effective and satisfactory methods 
of conserving soil moisture by means of tillage. 

In the study of the capillary movements of water it 
was seen that large amounts of moisture in many soils 
were being moved continuously from lower strata of 
soil to the upper zone to replace that which was being 
carried away in the atmosphere by evaporation. The 
water so removed is thus of no value to the crop, and is 
usually a serious loss. By destroying the capillary 
tubes that have formed close to the surface, the upward 
flow of moisture can be checked at this point and much 
loss of water be prevented. Frequent surface cultiva- 
tion, for this reason, has been shown to be very effective 
in promoting the growth of crops in semiarid sections 
of the country and in all sections during protracted dry 
spells. The shallow stirring of the earth breaks up the 
capillary tubes that have formed in the compacted sur- 
face and spreads a loose blanket of dry earth — a dust 
mulch — over the surface. 

Now in connection with this there are some questions 
that the farmer needs to have answered, such as : What 
depth of cultivation shows the best results in the con- 



STUDIES ABOUT SOILS 33 

servation of moisture ? How frequently should this cul- 
tivation be repeated to be most effective ? 

References: King, The Soil, pp. 184-190. Fletcher, Soils, 
pp. 90-92, 107-110. Snyder, Soils and Fertilizers, p. 27. 



Exercise 18 

Effect of Soil Mulches on Evaporation of Water from Soils 

Fill all" the tubes, with the same kind of soil, compacting each ^ 
three inches, and pouring enough water upon it to make it thor- 
oughly moist. Fill to within a half inch of the top, but do not 
pour water on the top. The enlarged bases of the tubes are then 
partially filled with water, and the tubes are left till the surface 
soil becomes moist. The tubes are then ready for use. As the 
water evaporates from the surface it must be replaced from day 
to day by refilling the base, the exact weight of water added in 
each case being noted. 

The loss of water is determined by the loss in weight of the 
tubes. Weigh each day. 

Tube 1, check (no cultivation).^ 

1 The tubes used for this experiment are made of light galvanized 
iron, and are 18 inches long and 6 inches in diameter. The bases are 
3 inches high and 8 inches in diameter. There is a rim round the top 
of the base, leaving an opening slightly larger than the tube. A col- 
lar is soldered around the tube 2f inches from one end, so that the 
tube, when standing in its base, rests on the collar, leaving |-iuch space 
between the end of the tube and the bottom of the base. A small 
tube, closed with a cork, is soldered to the rim of the base, through 
which water can be supplied as needed. 

2 Cultivate the soil each morning with a knife to the depth indicated, 
being careful to lose none in the operation, as this would destroy the 
accuracy of the weights taken. 



34 MANUAL OF AGRICULTURE 

Tube 2, cultivated 1 inch deep. 

Tube 3, cultivated 2 inches deep. 

Tube 4, cultivated 3 inches deep. 

Tube 5, cultivated 4 inches deep. 

The cultivations should be made every day to the required depth. 
Each tube has an area of 2 2 i^s 5 o ^^ ^^ ^^^^' ^^^ ^^^ results are to 
be computed in tons of water evaporated per acre per week. It is 
very necessary that the tubes all have the same exposure to heat 
and air currents. 

Upon what principle does a soil mulch conserve moisture ? 

What effect will cultivation have on a very wet soil ? 

If the water-table were 12 inches from the surface instead of 
24, what difference would there be in your results ? 

Is there any argument in the experiment in favor of fall plowing ? 

Does it show the value of cultivating as soon as possible after a 
heavy rain ? 



XVI. — Mulches of Various Materials 

For field crops of large areas the dust mulch secured 
by surface cultivation is probably the most practicable 
method of conserving soil moisture ; but on more re- 
stricted areas devoted to orchards, small fruits, and 
gardens, it is possible to employ artificial mulches of 
manure, straw, leaves, clippings from the lawn, saw- 
dust, peat, or sand. There are sometimes other ad- 
vantages than the conservation of moisture secured in 
the use of these mulches ; for instance, in the growing 
of some vegetables, such as potatoes, the protection of 
the roots and tubers from too intense heat seems to give 
good results. However, in Exercise 19 the thing to 



STUDIES ABOUT SOILS 35 

be determined is the relative effectiveness of artificial 
mulches of different materials. 

References : Fletcher, Soils^ pp. 90-91. Snyder, Soils and Fer- 
tilizers, p. 35. 

Exercise 19 

Effect of Artificial Mulches upon Evaporation of Water 
from Soils 

Fill tubes, as in preceding exercise, to within one inch of top, and 
then fill the remaining part with material for mulch. Proceed as 
in Exercise 18. 

Tube 1, check (filled to top with same kind of soil). 

Tube 2, one inch of sand. 

Tube 3, one inch of gravel. 

Tube 4, one inch of peat. 

Tube 5, one inch of sawdust or cut straw. 

The area of each tube is 221850 ^^^^• 

Compute loss of water in tons per acre per week and tabulate 
results. 

What will be the effect of these mulches on temperature ? 

What is the principle of the growing of "straw potatoes," i.e. 
covered with straw and not cultivated ? 

XVII. — Improvement of Heavy Soils by Use of Farm 
Manure 



We speak of clays as heavi/ soils and sands as 
soils, meaning not the relative weights of these soils, 
which is just the reverse of what the terms indicate, 
but that clays are plastic and sticky and difficult to 



36 MANUAL OF AGRICULTURE 

handle when moist, while sands are loose and crumbly 
even when wet. 

This characteristic of clay makes it a difficult and 
often unpleasant soil to cultivate, since one must ex- 
ercise great care and judgment in not tilling it when it 
is too wet, and if it becomes too dry before working, it 
bakes so solidly that it can only be broken up into 
lumps, so that often no amount of labor can get the soil 
into good condition for cropping that season. 

This undesirable quality in clays is due to the fine- 
ness of their particles, which allows them to pack too 
closely together. As was demonstrated in Exercise 6, 
the application of lime to such soils causes the fine 
particles io flocculate and form larger crumbs of material, 
which gives a looseness to the soil and helps to modify 
its plasticity. 

Another way to treat clay soils to make them lighter 
and more porous in texture is to mix with the soil a 
dressing of manure, leaf mold, or some other form of 
organic matter. 

The work in Exercise 20 is to demonstrate the bene- 
ficial effects of working organic matter into heavy clay 
soils, and to get some idea of the approximate amounts 
that should be used in order to change materially their 
character. 

References : Fletcher, Soils, pp. 322-327. Snyder, Soils and 
Fertilizers, pp. 93-96. 



STUDIES ABOUT SOILS 37 

Exercise 20 
Tlie Effect of Organic Matter on Baking of Clay Soils 

Use four one-gallon earthen jars provided with drainage outlets, 
and fill them to within one inch of the top as follows : — 

No. 1. Clay. 

No. 2. Clay thoroughly mixed with 5 per cent of peat by 
weight. (Fine, dry, well-rotted manure may be used.) 

No. 3. Clay thoroughly mixed with 10 per cent of peat or 
manure by weight. 

No. 4. Clay thoroughly mixed with 20 per cent of peat or 
manure by weight. Apply enough water to saturate the soil, using 
the same amount in each jar, and expose all the jars to the direct 
rays of the sun until the soil is baked. 

Test the soils in the four jars to compare the ease with which 
the crust can be pulverized with the fingers. 

Write out fully the results of this exercise. 

What causes a clay soil to bake ? 

In what way does the crust thus formed injure growing plants ? 
How can a farmer prevent the baking of his soil ? 



PART II. —STUDIES ABOUT CROPS 

XVIII. — What Foods Plants Use and How They 
are Obtained 

In the first twenty exercises of the Manual the study 
and experiments have had for their object a better 
understanding of the physical properties of the soil in 
its environmental relations to the plant. 

The soil is called the home of the plant, inasmuch as 
it is its natural abiding place throughout its life, furnish- 
ing a spot for the anchorage of its roots, where they 
may find congenial surroundings as regards moisture, 
heat, and air, and a firm support from which to lift their 
aerial parts and expose the leaf surfaces to the air. 

It is the business of the farmer to know what are the 
needs of the plant in these respects, and then how to 
manage his soil to secure in the fullest degree possible 
the conditions required. 

But the important work of the plant is to grow — to 
take into its tissues certain substances that lie outside 
it, to transform these into its own substance, and to 
build them up into its various parts, thus enlarging and 
developing itself to its perfect stature and the comple- 
tion of its life's functions. 

What, then, are these substances which the plant uses 
for its building materials, and from what sources does 

39 



40 MANUAL OF AGRICULTURE 

it obtain them ? These questions open up a new and 
broad field for the farmer's investigation. 

Briefly stated, these are the answers that are now 
generally accepted for the above question: — 

1. There are but ten elements which the plant re- 
quires for complete development of all its parts. These 
are carbon, oxygen, hydrogen, nitrogen, phosphorus, 
potassium, calcium, sulphur, magnesium, and iron. The 
symbols used to represent these elements, in the order 
in which they have been named, are C, O, H, N, P, K, 
Ca, S, Mg, and Fe. 

There are two ways of determining the substances 
which plants require for the building of their parts. 
One way is to analyze the plants and so learn of what 
materials they have been made. In all plants analyses 
always show the presence of the ten elements that have 
been named. Usually a few other elements — silicon, 
chlorine, and sodium most frequently — are found pres- 
ent in the composition of the plants. 

The second way is by synthesis — to grow plants 
either in distilled water or in pure sand, which insures 
that the growing plants get no plant food except what 
the grower gives to them and what they secure from 
the air. By this method it is demonstrated beyond all 
doubt that no plant can attain perfect development if 
not supplied with all of the ten elements, C, O, H, N, 
P, K, Ca, S, Mg, and Fe, and that the omission of any 
or all other substances in no way retards growth. 

Moreover, in answer to the second question, as to the 
sources from which plants get their supplies of these 



STUDIES ABOUT CROPS 41 

essential foods, the investigations of scientists have 
shown that all the carbon and part of the oxygen used 
by the plant are taken from the air as the gaseous com- 
pound, carbon dioxide (COg), which enters the plant 
through minute openings in its leaves called stomata. 
The hydrogen and the remainder of the oxygen which 
the plant takes up are secured from the soil in the form 
of water, which is a compound of these two elements 
(HgO). All substances which plants take up as foods 
— with the one exception, carbon dioxide — come from 
the soil and entejx the plants through their roots in 
liquid form. That is, the hydrogen and oxygen are 
the elements of which the water is composed, and the 
nitrogen, phosphorus, potassium, calcium, sulphur, mag- 
nesium, and iron must all exist in the soil as soluble 
compounds, — solids like salt and sugar that dissolve 
more or less readily in the water in the soil, — and so 
the plants obtain them in solutions with the water 
absorbed by their roots. 

This statement again emphasizes the lesson of so 
many previous exercises — the immense importance of 
an abundant supply of water for the crops, since water 
not only contains two of the essential plant foods, but 
is also the solvent and carrier of seven of the other 
eight. Six of these seven elements — phosphorus, po- 
tassium, calcium, sulphur, magnesium, and iron — are 
mineral compounds, locked up in the soil as constitu- 
ents of the rocks. Nitrogen, however, is never found 
as an element in the composition of any of the rocks ; 
its source as plant food in the soil exists in the various 



42 MANUAL OF AGRICULTURE 

organic compounds obtained from decaying animal and 
plant tissues — the humus of the soil. 

Since nearly four fifths of the atmosphere is free 
nitrogen, it was first thought that plants secured their 
nitrogen, as they do their carbon, directly from the air. 
But this was long ago disproved, though the belief 
continued that the ultimate source of nitrogen in all 
organic compounds was the limitless supply of it in the 
air. This is now known to be true, and the claim has 
been made that no other discovery in the science of 
agriculture promises to yield results of such importance 
to the farmers as this : that there are certain forms of 
soil bacteria which have the power to take the free 
nitrogen directly from the air and build it into com- 
pounds that the plants can use. 

Moreover, it has been discovered that these minute 
organisms make their homes and perform this work only 
on the roots of a certain kind of plants called legumes, 
which are best represented among our crops by the 
garden and field peas and beans, cowpeas, soy beans, 
the various kinds of clover and alfalfa. For each vari- 
ety of leguminous plant there is a separate variety of 
bacteria which will live on the roots of this particular 
legume and on no other. (The one known exception 
to this statement is found in the case of the germs that 
live on the roots of alfalfa. These also thrive on sweet 
clover, which has been generally regarded as a weed.) 

The presence of these bacteria in a soil is indicated 
by the little tubercles that grow on the roots of the 
legume that serves as the host plant for these organ- 



STUDIES ABOUT CROPS 43 

isms. These tubercles are the homes of colonies of 
the bacteria — millions of them in a single tubercle. 
The bacteria are thought to live on the juices of the 
plant's roots, and in return they furnish the plant witli 
the nitrogen which they have the power to take from 
the air that permeates the soil about the roots of the 
plant. In this way the plant is not dependent for its 
nitrogen upon the supply in the soil, and when the crop 
is plowed under, or fed, and the manure returned to the 
field, an addition of this essential and expensive plant 
food is made to the soil without extra cost to the farmer. 
Exercise 21 is the first of a number of exercises given 
in the Manual to teach some of the principles of soil 
fertility. The objects of this exercise are : — 

(1) To show that nitrogen, phosphorus, and potas- 
sium are essential plant foods, and if the plant is de- 
prived of any one of them it cannot complete its 
growth. 

(2) To show the power of the nitrogen-gathering 
bacteria to supply the host plant with nitrogen taken 
from the air. 

This experiment is believed to be one of the most 
valuable and practical exercises given in the course, 
and wherever a school can plan to conduct it, the 
classes should carry it through. 

References : Johnson, How Crops Feed, pp. 251-375. Johnson, 
How Crops Grow, pp. 126-220. Snyder, Soils and Fertilizers, 
pp. 57-229. Voorhees, Fertilizers, pp. 38-98. 



44 MANUAL OF AGRICULTURE 

Exercise 21 

Soil Fertility 

To SHOW THAT CERTAIN PlAXT FoODS ARE ESSENTIAL 

Preparation of Pot Cultures 

Use clean white sifted sand in 5-liter heavy glass battery jars, 
having 1 centimeter hole within 1 centimeter of the bottom. Into 
the hole fit a drain tube made of glass tubing with a glass-wool 
filter at the inner end, so that it will take liquid from the lowest 
place in the jar. Put up two series of eight of these pots. 

To extract the sand, fill the jar within 1 centimeter of the 
top with dry sifted sand and add to this dilute sulphuric acid 
(made by adding 100 cubic centimeters of concentrated chemically 
pure sulphuric acid to 900 cubic centimeters of ammonia-free 
water) until the sand is saturated. Let stand two hours, and 
then add ammonia-free water, allowing the drainage to flow into 
a second jar until it is saturated. Allow this jar to stand two 
hours, and then wash both with ammonia-free water until free 
of acid, as shown by tests with litmus paper. In this way any 
soluble plant food is removed from the sand. One portion of 
acid extracts two jars. The sand for two of the jars, in which 
experiments are to be made to show the effect of nitrogen -gather- 
ing bacteria, is first heated to 120°-L30° C. for half an hour, 
and then extracted and washed as above. 

Before planting, mix with the sand of each pot 10 gi'ams of 
pure calcium carbonate to neutralize any possible acidity remaining. 

In making applications of plant food, as indicated in the follow- 
ing table, and in such amounts as are there shown, the solutions to 
be applied to each pot are to be mixed together, and diluted to 
1000 cubic centimeters. Mix thoroughly, and apply the whole 



STUDIES ABOUT CROPS 45 

amount to the pot, allowing any water present to be forced out 
through the drain. 

The first application of the plant-food solutions is to be made 
at the time of planting, the second three weeks later, the third two 
weeks later, and subsequent applications at intervals of one week, 
each time as directed above. 

Preparation of Plant-food Solutions^ 

Solution No. 1. Nitrogen : Dissolve 80 grams of ammonium 
nitrate in 2500 cubic centimeters of distilled water.^ Use 10 cubic 
centimeters per pot. 

Solution No. 2. Phosphorus : Dissolve 25 grams of mono- 
calcium phosphate in 2500 cubic centimeters of ammonia-free 
water. Use 10 cubic centimeters per pot. 

Solution No. 3. Potassium : Dissolve 50 grams of potassium 
sulphate in 2500 cubic centimeters of ammonia-free water. Use 
10 cubic centimeters per pot. 

Solution No. 4. Magnesium : Dissolve 20 grams of magnesium 
sulphate in 2500 cubic centimeters of ammonia-free water. Use 
10 cubic centimeters per pot. 

Solution No. 5. Iron: Dissolve 0.1 gram ferric chloride in 
2500 cubic centimeters of ammonia-free water. Use 1 cubic cen- 
timeter per pot. 

Prepare these solutions carefully, using chemically pure salts, and 
label each bottle. 

For inoculating the sand in pot 8 with bacteria, obtain about 
a pound of soil from a field where there has recently been growing 

1 The instructor in chemistry should prepare these solutions for 
Exercise 21. 

2 If it is not convenient to prepare distilled water in a laboratory, 
pure rain water may be used in this experiment, both for washing the 
sand and watering the plants. 



46 



MANUAL OF AGRICULTURE 



Pot 

No. 


Pbeparation of 
Sand. 


Plant Food 
Added, 


Seeds Planted. 


1 


Extract and wash 


None 


Corn or Soy Beans 


2 


Extract and wash 


All but N 


Corn or Soy Beans 


3 


Extract and wash 


All but P 


Corn or Soy Beans 


4 


Extract and wash 


All but K 


Corn or Soy Beans 


5 


None 


All 


Corn or Soy Beans 


6 


None 


All 


Red Clover, Soy Beans, or 
Alfalfa 


7 


Heat, extract, and 


All but N 


Red Clover, Soy Beans, or 




wash 




Alfalfa 


8 


Heat, extract, and 


All but N 


Red Clover, Soy Beans, or 




wash 


Bacteria 


Alfalfa 



the same legume which is to be used in this experiment, being 
sure that tubercles were present on the roots. Put this soil in a 
glass fruit jar and shake thoroughly with about one quart of pure 
water. Then let settle, and as each seed is planted add 10 cubic 
centimeters of the clear liquid before covering the seed. 

Why is CaCO 3 added ? Why are two of the pots heated ? 

Observe each week, and make observations about differences of 
growth and appearance. 

Thin the corn and bean plants to three in each pot and the clover 
plants and alfalfa to ten. 

The pots should stand where the heat and light conditions are 
favorable for rapid growth, and where all conditions except those 
controlled in the application of plant-food solutions are the same for 
every plant. 

XIX. — Farming in Four-gallon Pots 

In Exercise 21 tlie plants were grown in glass bat- 
tery jars filled with sand from which all plant food had 



STUDIES ABOUT CROPS 47 

been extracted. In this way complete control of the 
food conditions is secured in studying the effects of 
the omission of any particular element, because it was 
known exactly what foods were furnished for the plant 
and what was lacking. 

Notice that in the experiments the tests are confined 
to the elements nitrogen, phosphorus, and potassium. 
The reason is that these are the only plant-food ele- 
ments about which the farmer usually needs to con- 
cern himself. The supply of carbon dioxide in the 
air, though it constitutes not more than 6 parts in 
10,000 of the atmosphere, is always sufficient to meet 
the needs of the crop for carbon and oxygen, and the 
question that demands the attention of the farmer here 
is only that of preserving an abundant and healthy leaf 
surface for his growing crops. 

From the water contained in the soil the hydrogen, 
and more oxygen, are obtained. Sulphur, magnesium, 
and iron are used by plants in small amounts as com- 
pared with the other foods, and most soils contain 
enough of them to meet crop requirements for thou- 
sands of years. The demand for calcium as a plant 
food is not large, but many soils are more or less acid, 
and these need applications of lime to correct this 
condition. 

In the case of nitrogen and phosphorus, however, 
and to a less degree in Illinois, of potassium, the amounts 
of these elements which are removed from the soil in 
large crops, as compared with the amounts shown by 
analyses to be contained in the surface foot of most of 



48 MANUAL OF AGRICULTURE 

these soils, are so great that maintaining a sufficient 
supply of some or all of these three elements in the 
soils to make possible the raising of maximum crops 
for any number of years becomes a serious problem in 
soil fertility. 

In the pot-culture work of Exercise 22 regular field 
soils are used, the object being to test the needs of the 
soils selected for whatever crop is being grown in re- 
spect to the three plant foods, — N, P, and K. 

The amounts of the fertilizers used in each pot are 
carefully computed on the basis of the amounts of each 
element, which are removed from an acre by maximum 
crops, i.e. 100 bushels of corn, 100 bushels of oats, 50 
bushels of wheat, etc. 

Pots 1, 5, and 10 are used as checks for the purpose 
of comparison. The difference between the yield of 
pot 2 and the average of the yields of pots 1, 5, and 10 
will indicate the soil's need of nitrogen. In the same 
way the question is asked in pot 3 for phosphorus and 
in pot 4 for potassium. 

It may happen that there is a deficiency of plant 
food in two elements, or even three, and in this case 
there can be no material increase in the yields until 
all the food requirements of the crop are met. These 
points will be settled by the tests made in pots 6, 7, 8, 
and 9. 

A regular plant house or conservatory is, of course, 
the best place for pot-culture work, but these exer- 
cises can be used wherever house plants can be grown. 
One thing is very essential — all pots must be given 



STUDIES ABOUT CROPS 49 

exactly the same treatment as to soil, moisture, heat, 
light, and planting, the only condition in which there 
is a difference being the application of plant food. 

References : Johnson, How Crops Feed, pp. 251-375, Johnson, 
Hoio Crops Grow, pp. 126-220. Snyder, Soils and Fertilizers, pp. 
57-229. Voorhees, Fertilizers, pp. 38-98. 



Exercise 22 
Applicatioris of Plant Food for Crop Production 

Use four-gallon earthenware pots in series of ten pots for each 
crop. The pots should have holes in the bottoms for drainage. 
Fill another pot of smaller diameter, heaping it full of sand, and 
turn over this the pot in which you wish to make a hole, so that 
the bottom on the inside rests on the sand. Then with a sharp 
punch and a few light blows of a hammer a hole can be easily made. 

FiU the ten pots of each series with the same soil, taking it from 
the field which you wish to test for the crop you are going to grow, 
as oats, barley, wheat, red clover, alfalfa, sugar beets, or any of the 
garden crops. 

In collecting the soil for the pots, take it from the upper 
seven inches, which is about the depth of the usual plow line.^ 

Apply the plant foods according to directions given below : — 

1. None (check). 

2. Nitrogen. 

1 To make the conditions follow more closely field conditions, two 
collections of soil should be made as follows : Remove the soil which 
is to be used in the experiment to the depth of 7 inches and place 
it in a box. Then put into a second box the soil underlying this in the 
stratum from 7 to 12 inches below the surface. In filling the pots, use 
soil from the second box for the bottom, and on 5 inches of this 
place the surface soil from the first box. 



50 MANUAL OF AGRICULTURE 

3. Phosphorus. 

4. Potassium. 

5. None (check). 

6. Nitrogen, phosphorus. 

7. Nitrogen, potassium. 

8. Phosphorus, potassium. 

9. Nitrogen, phosphorus, potassium. 
10. None (check). 

For applications of nitrogen, use ^ ounce (16 grams) of dried 
blood per pot ; for phosphorus, use ^ ounce (8 grams) of steamed 
bone meal; for potassium, use ^ ounce (4 grams) of potassium 
chloride. Mix the plant food thoroughly with the soil in the pots 
to the depth of 7 inches, a few days before the seeds are to be 
planted. 

The pots used in these exercises are 10| inches in diameter and 
11 J inches deep (inside measurements). This gives a surface area 
for each pot of about -jtw^ ^^ ^^ ^^^^' ^^ ^^^^ ^^® gram application 
of plant food, or every gram of yield of crop, corresponds to one 
pound per square rod, or 160 pounds per acre. 

XX. — Experiment-field Work for High Schools 

The University of Illinois Experiment Station now 
has twenty -three experiment fields distributed over all 
parts of the state. Each year interest in the work 
done on these fields has increased, not alone among 
those directly engaged in farming, but among all classes 
of people who are beginning to recognize their educa- 
tive value. 

Within the past year a number of high schools have 
been provided with land to be used in teaching agri- 
culture. These school fields generally range in size 



STUDIES ABOUT CROPS 51 

from five to ten acres. In some cases the land has been 
given to the school, in others it has been bought or 
rented by the district, and in still other cases a land- 
owner interested in having agriculture taught in the 
school has donated the use of as much land as the school 
needs for the purpose. 

Dr. C. G. Hopkins, Professor of Agronomy, Univer- 
sity of Illinois, and Chief of Agronomy of the Agri- 
cultural Experiment Station, offers to assist any schools 
in the state that wish to establish experiment plots in 
the laying out of their plots and the planning of the 
work to be done on them. 

Already two or three high schools have availed them- 
selves of this offer, and their fields have been plotted for 
school work. There is reason to believe that popular 
sentiment favoring this branch of school work is so 
strong that it will not be difficult for any high school 
to secure enough land to establish an experiment field 
to be used in connection with its courses in agriculture. 

This work with the plots does not duplicate the pot- 
culture work given in Exercise 22, though each may be 
regarded, in a way, as a complement of the other. 

In the work with the pots certain tests may be made 
that require a more complete control of conditions than 
can be secured in field work. On the other hand, in 
the experiments on the plots, the crops are grown under 
the natural conditions with which the farmer deals, and 
on a scale sufficiently large to make it possible to com- 
pare results with those on tlie surrounding farms. If 
the work is carefully planned in the beginning, and then 



52 MANUAL OF AGRICULTURE 

the plans are followed and the results obtained each 
year are kept as a permanent record, the experiment 
plots will every year increase in interest and usefulness 
as a part of the school work in agriculture. 

The outlines of the work given in Exercises 22 and 23 
were prepared by Dr. Hopkins, and were published in a 
leaflet a few years ago. Exercise 21 is taken from 
Laboratory Manual for Soil Fertility^ by Dr. Hopkins 
and Professor J. H. Pettit, where it is given as Practices 
16 and 17. 

References : Johnson, How Crops Feed, pp. 251-375. Johnson, 
How Crops Grow, pp. 126-220. Snyder, Soils and Fertilizers, pp. 
57-229. Voorhees, Fertilizers, pp. 38-98. 

Exercise 23 

Plot-culture Tests to Determine the Plant Food Requirements 
of the Soil 

The size of the plots to be used will be determined by the amount 
of land available for this work. 

Where the area is restricted, the plots may be laid off in rec- 
tangles 1 rod by 2 rods and separated from each other by sunken 
paths not less than 2 feet wide. This will give each plot an area 
of one square rod (yj-g- of an acre). If the school possesses more 
land, larger plots up to tenth acres (2 rods wide and 16 rods long), 
with half-rod strips separating them, may be laid off, as is done on 
the experimental fields at the University. 

The plant-food applications for the smaller plots (one square 
rod), to be made annually, are as follows : — 

Plot No. 1. None (check). 

Plot No. 2. Nitrogen. 



Plot No. 


3. 


Plot No. 


4. 


Plot No. 


5. 


Plot No. 


6. 


Plot No. 


7. 


Plot No. 


8. 


Plot No. 


9. 


Plot No. 


10. 



STUDIES ABOUT CROPS 53 

Phosphorus. 

Potassium. 

None (check). 

Nitrogen, phosphorus. 

Nitrogen, potassium. 

Phosphorus, potassium. 

Nitrogen, phosphorus, potassium. 

None (check). 

Apply the nitrogen in the form of dried blood, 16 pounds per 
square rod ; phosphorus as steamed bone meal, 8 pounds per square 
rod ; potassium as potassium chlorid, 4 pounds per square rod. 
The plant foods should be well worked into the soil to the depth 
of about 7 inches a few days before planting, care being taken 
not to mix the soils from adjacent plots. 

Several different field and garden crops should be planted in rows 
across all of the ten plots. Oats, barley, wheat, clover, alfalfa, etc., 
can be planted in rows 8 inches apart, dropping the seeds about 1 
inch apart in the row ; radishes, lettuce, carrots, beets, peas, etc., 
in rows 16 inches apart; sweet corn, potatoes, eowpeas, soy beans, 
etc., in rows 32 inches apart; field corn in rows 40 inches apart; 
and cucumbers and melons 64 inches apart. 

A marker with five runners 16 inches apart is easily made of 
boards, and it will serve to mark good straight rows across all of 
the plots for all crops. 

By this system of planting every crop will be represented on 
every plot, and the elfect of all of the diff'erent kinds of soil treat- 
ment can be noted on each crop. 

If the complete experiment cannot be undertaken, a fairly satis- 
factory experiment can be made by using only the first five pots 
or plots. 

In planning these soil-fertility experiments, it is well to bear in 
mind that very sandy soil is likely to be most deficient in nitrogen. 



54 MANUAL OF AGRICULTURE 

In ordinary Illinois soil, especially that which has been under cul- 
tivation for many years with clover in rotations, the element phos- 
phorus is most deficient. In peaty soils, potassium is most de- 
ficient. 

In drawing conclusions from results which may be obtained in 
these experiments, it should be understood that while we may ap- 
ply purchased nitrogen in order to obtain information quickly as 
to the needs of the soil, the nitrogen should be obtained in all gen- 
eral farming by the slower process of growing leguminous crops 
which, when provided with the proper bacteria, can get nitrogen 
from the air. 

The three plant-food elements, nitrogen, phosphorus, and potas- 
sium, are contained in most soils in rather small amounts. In- 
deed, it often happens that the soil furnishes so little of one or 
more of these elements that the plant suffers for that kind of food. 
In such cases we can grow larger crops by giving the plant the 
food it needs. 

To find what elements of plant food are most deficient in the 
soil, we should experiment and see what etfect is produced on 
the growth of plants by adding different plant-food elements to 
the soil. 

For nitrogen, dried blood should be applied. This contains 
from 12 to 14 per cent of nitrogen in a form which is not likely to 
injure the plant, even if used in some excess. A 100-pound bag 
of ground dried blood can be obtained from Swift & Company, 
Union Stock Yards, Chicago, for about $2.50. 

For phosphorus, steamed bone meal should be applied. The 
best steamed bone meal contains from 12 to 14 per cent of the 
element phosphorus in a very good form for plants. A 100-pound 
bag of extra fine ground steamed bone meal (" Big Six " brand) 
can be obtained from Morris & Company, Union Stock Yards, 
Chicago, for about $1.25. 



STUDIES ABOUT CROPS 55 

For potassium, use potassium chlorid. This is a salt which 
usually contains from 40 to 42 per cent of the element potassium. 
A lOO-pound bag of potassium chlorid can be obtained from 
Armour Fertilizer Works, Union Stock Yards, Chicago, for about 
$2.50. 

The Armour Fertilizer Works, Union Stock Yards, Chicago, 
have agreed to furnish a one-pound package of potassium chlorid, 
a two-pound package of fine ground steamed bone meal, and a 
four-pound package of ground dried blood for a total charge of 
seventy-five cents, the purchaser to pay express charges. 

These quantities are ample for pot-culture experiments. 

XXI. — Questions relating to the Seeding of Crops 

There is found among farmers to-day a great differ- 
ence of opinion — or a great indefiniteness of opinion 
— about the quantity of seed per acre in the various crops 
that should be sown to give best results. In the case of 
oats, for instance, is it better to make a thin seeding to en- 
courage the tendency of the plants to tiller, or will heavier 
yields of better quality of grain be secured by planting 
so thickly that each seed will produce but a single 
stalk and head ? There are as strong adherents to the 
one practice as to the other. 

It may be that experimental work on such subjects by 
school classes in agriculture will add little to the sum of 
knowledge which we already have about it; but it is 
by becoming interested in work of this kind that men 
are trained to think independently and to form definite 
opinions, supported by scientific principles and personal 
experience. Such work as is given in Exercises 24 and 



56 MANUAL OF AGRICULTURE 

25 has been found very profitable in the agricultural 
schools in Canada. 

The work is not at all difficult for a class to handle, 
but it will require care and thought. The seed should 
first be tested to determine its vitality. The pupils 
will find that some samples of oats will contain very 
many more grains in a bushel than others. This raises 
other questions for them to consider. For example : — 
Shall more or less seed be sown on fertile soil than on 
one that contains less plant food ? Such problems con- 
cern alike the farmer and the student. 

Keference : Hunt, The Cereals in America^ p. 302. 

Exercise 24 

Crop Production: Oats 

To Determine what Amount of Seed per Acre gives 
Best Results 

On a series of 10 plots of one square rod each, in which all con- 
ditions are similar, except the amount of seed used, make seedings 
of oats as follows : — 

Plot 1. Sow Si ounces (rate of 1 bushel per acre). 

Plot 2. Sow 4i ounces (rate of li bushels per acre). 

Plot 3. Sow 4:^ ounces (rate of 2 bushels per acre). 

Plot 4. Sow 8 ounces (rate of 2i- bushels per acre). 

Plot 5. Sow 9 1 ounces (rate of 3 bushels per acre). 

Plot G. Sow 11 1^ ounces (rate of 3|^ bushels per acre). 

Plot 7. Sow 12i ounces (rate of 4 bushels per acre). 

Plot 8. Sow 14| ounces (rate of 4.1- bushels per acre). 

Plot 9. Sow 16 ounces (rate of 5 bushels per acre). 

Plot 10. Sow 17 J ounces (rate of 5.V bushels per acre). 



STUDIES ABOUT CROPS 57 

Make the drills 8 inches apart and cover li to 2 inches deep. 
During the season of growth observe the differences in the tendency 
of the plants to " stool " due to thickness of planting. 

When ripe, harvest each plot separately and thresh with a flail. 
Weigh and record the yields of each plot, giving their acre equiva- 
lents. 

XXII. — Methods of Sowing Grains 

Another question relating to the growing of oats and 
other spring grains, which still remains unsettled in the 
minds of many farmers, is whether drilling or broad- 
casting is the better way to sow the seeds. The one 
method insures a more perfect covering of the seed at 
a uniform depth ; the other may give a more even dis- 
tribution of the grain over the whole surface at less 
cost for labor and machinery. It is a good experiment 
for classes in agriculture to work on. Of course, the 
results of a single season cannot settle the matter. 
There are so many conditions that affect the growing 
of a crop which are seasonal, and differ from year to 
year, that it will require the results of many tests to 
give any reliable basis on which to form conclusions ; 
but if these experiments were continued in a school 
year after year, and the records were taken accurately 
and left for succeeding classes to use and extend, it is 
certain the work could be made worth while. 

References: Hunt, Tlie Cereals in America^ pp. 131, 296, 304. 
Dondlinger, The Book of Wheat, pp. 65-69. 



58 MANUAL OF AGRICULTURE 

Exercise 25 

Crop Production : Oats 
Test of Drilling versus Broadcasting 

Lay off four plots of one square rod each and prepare them all 
for seeding in the same way, then sow oats as follows : — 

Plot 1. Sow 4| ounces (1|- bushels per acre) in drills 8 inches 
apart and cover 1^2 inches deep. 

Plot 2. Sow 4| ounces (1^ bushels per acre) broadcast and cover 
with a garden rake. 

Plot 3. Sow 6f ounces (2 bushels per acre) in drills 8 inches 
apart and cover 1|— 2 inches deep. 

Plot 4. Sow 6f ounces (2 bushels per acre) broadcast and cover 
with a garden rake. 

Observe differences in growth between the oats drilled and those 
sown broadcast. 

Harvest and thresh crops on each plot separately and record the 
yields, giving results in acre equivalents. Write conclusions. 

XXIII. — Special Treatment of Seed 

The farmer who would succeed in the work of grow- 
ing crops must not only know how to prepare and treat 
the soil, how to breed and select seed, how to plant the 
seed and cultivate the crop, but he must also know 
how to protect the growing plants from the many forms 
of insect enemies and fungus diseases which seem to be 
increasing from year to year in numbers and destruc- 
tiveness. 

A disease which is very common in oat fields and 
much more serious in its effects upon the yield of the 



STUDIES ABOUT CROPS 59 

crop than most farmers realize is smut. There are two 
forms of this disease : loose smut, which attacks the 
whole head and turns it into a black mass of spores ; 
and closed smut, which affects only the kernels, and is 
not so easily seen. 

If the farmer were helpless in combating this enemy, 
it might be well to let him remain ignorant of the 
amount of the loss it causes him. Professor Zavitz, of 
the Ontario Agricultural College, who has conducted 
experiments for many years in growing and improving 
oats, says that in many fields the loss from smut 
amounts to 40 per cent or more. A few years ago a 
careful investigation of the oat fields of Wisconsin was 
made through the assistance of graduates of the College 
of Agriculture, and it was found that 17 per cent of the 
crop that year was destroyed by smut. 

And yet there are two simple and inexpensive treat- 
ments by which this disease can be completely pre- 
vented. It is the purpose of Exercise 26 to familiarize 
the students with these methods of treating the seed 
which are now known to be effective in safeguarding 
the crop from smut. There would be an increase to 
the country annually of millions of bushels of oats if 
the farmers could be taught to use one of them. 

Since the spores of the fungi which cause the smut 
in oats are attached to the seed and develop in the grow- 
ing stem of the plant until the head appears and is 
ready for their attack upon it, any treatment of the 
seed which will kill these spores and not injure the 
vitality of the grain for seed purposes will be effective, 



60 MANUAL OF AGRICULTURE 

and two such treatments are given for practice in Ex- 
ercise 26. 

Students will be impressed with the extent and 
seriousness of this disease if they make inspections of 
oat fields to determine the per cent of the crop that is 
affected by it. Let each student provide himself with 
a lath frame having an area of one square foot. In 
different parts of the field in which the examination is 
being made, place this frame on the ground, count the 
numbers of stems of oats inclosed by the sides of the 
frame, and also the number of stems bearing heads 
affected by smut. In this way, by finding the average 
of the fractions showing the proportion of diseased 
heads to sound ones, a fairly accurate determination 
of the per cent of loss in this oat crop caused by smut 
can be made. 

On fields or plots where tretited seed is used, leave a 
narrow strip for comparison,- and here sow untreated 
seed. Then find the per cents of diseased heads of oats 
where the two kinds of seeds were used. A comparison 
of these records should be conclusive proof of the value 
of treating seed oats for smut. 

Exercise 26 

Treating Seed Oats for Smut 

First Method 

On a tight floor spread a few bushels of the seed to be treated. 
Make a solution of concentrated formalin (a forty per cent solu- 
tion of formaldehyde), using one pint of the formalin to forty gal- 



STUDIES ABOUT CROPS 61 

Ions of water. Apply this solution to the oats with an ordinary 
sprinkling pot, wetting the top of the pile, then stirring the grain 
with a shovel and continuing the sprinkling and stirring until 
every kernel is thoroughly moistened. Now shovel the grain into 
a pile and cover with a blanket or sacks for about 12 hours to 
prevent too rapid evaporation of the formalin. 

Then uncover and shovel the pile over two or three times, and 
the seed will be dry enough to sow. 

The price of formalin is from sixty to eighty cents a pint, and the 
treatment of the seed will cost from two to four cents a bushel. 

Second Method 

Have two vessels — large tubs or barrels are best — and fill them 
nearly full of hot water. Let the water in one vessel be at a 
temperature of 110°-120° F., and in the other 132°-133° F. 
Have near at hand a bucket of cold water and a kettle of 
boiling water to use in keeping the liquid in the large vessels 
at the required temperatures. 

Put a bushel of oats in a sack and dip it into the water at 
110°-120° F. Leave it a minute for the mass to become warmed 
through, then change it to the other vessel of water at 132°- 
133° F. Keep a thermometer in the water, and should the 
temperature rise or fall, control it by adding cold or hot water, 
as may be needed. 

Every two or three minutes raise the sack of grain out of the 
water and lower it again. This will aid to saturate the whole mass 
thoroughly. 

Keep the seed in the hot water for ten minutes, then spread out 
on a floor and dry sufiiciently for sowing. Repeat with as many 
bushels as are needed. Each of these methods of treating the seed 
for smut, if the work is done thoroughly, will kill all the pores and 
completely protect the crop from this disease. 



62 MANUAL OF AGRICULTURE 

XXIV. — Studies with Corn 

In many ways corn is much the most satisfactory of 
all crops for class study and experiment work. It is 
planted and makes considerable growth in the spring 
before the close of the school year, and its season is so 
long that it is still standing and maturing its grain 
when school work begins again in the fall. 

Being planted in open rows, it is easy of access for 
observation and experiment work. Cultivation plays a 
larger part in the growing of corn than it does with 
our other important cereals, and for this reason the suc- 
cess of the crop is more dependent upon the care it re- 
ceives during the growing season than in the case of 
the other grains. 

Moreover, it is the greatest wealth-producing crop in 
the United States; and hence especial attention is being 
given to the improvement, selection, and care of seed 
and to methods of cultivation. 

The structure of the plant also lends interest to its 
study. The fact that the stamens, which are the pollen- 
bearing organs of the corn plant, are produced on the 
top part of the stalk, — the tassel, — while the pistils, 
the other essential organs of the flower, — in corn called 
the silk, — are where the ear is borne makes it possible 
for the corn breeder to control the matter of inbreeding 
and self-fertilization and to a large degree determine 
the parentage of each kernel of corn. 

In the case of corn, as with oats, wheat, and other 
small grains, there is much uncertainty of opinion as to 



STUDIES ABOUT CROPS 63 

the proper thickness of planting and width of rows. 
Many experiment stations are working on this problem, 
and the results of their tests will be published later. 
Probably the particular value that work such as that 
outlined in Exercise 27 will have in school agriculture 
will come from directing attention to the importance 
of the farmer's having some definite knowledge on such 
questions as a guide to farm practices, and in the train- 
ing that it gives to those who are to manage farms and 
who should know how to settle these problems for 
themselves. These are matters that directly affect the 
profits of farming; and it is good training to teach the 
pupils that agriculture is a business full of problems to 
be settled, and that those who make it a success must 
know how to handle them. 

In considering the thickness of planting and the best 
distance between the hills, try to determine whether it 
is largely a question of sufficient supply of plant food 
in the soil, a more even distribution of corn roots 
through the whole area covered, or the best exposure of 
the plants to sunlight and air. 

Reference : Hunt, The Cereals in America, pp. 227-234. 



Exercise 27 

Crop Production : Corn 

To Determine how close to plant Corn 

Prepare five plots of one square rod each for corn, making the 
conditions alike for all plots ; then plant as follows : — 



64 MANUAL OF AGRICULTURE 

Plot 1. Hills 4 feet X 3 feet, 4 stalks in a hill. • 

Plot 2. HiUs 4 feet x 1 foot, 1 stalk in a hill. 

Plot 3. Hills 31 feet X 31 feet, 3 stalks in a hill. 

Plot 4. Hills 3 feet X 3 feet, 3 stalks in a hill. 

Plot 5. Hills 3 feet X 3 feet, 2 stalks in a hiU. 

Before planting, the seed should be carefully tested for ger- 
mination, and on plots (1), (3), (4) plant five grains, and a few days 
after the corn is through the ground, thin to the required num- 
ber. On plots (2) and (5) plant three grains, and thin as required. 

When the corn is mature, husk and weigh, giving the yields of 
each plot reduced to acre equivalents. 



XXV. — Problems in Cultivating Corn 

In growing corn it is an almost universal practice to 
cultivate the soil between the hills, from the time the 
plants are through the ground so that the rows can be 
seen until the}^ are too large to permit a team to be 
used, and then in many cases some cultivation is done 
later by hand with the hoe. 

The method of cultivation employed to-day and the 
implements that are used in cultivating corn now differ 
widely from those of a generation ago ; but in those 
days, as at the present time, a large factor in the cost 
of growing the crop was in the tillage that was believed 
to be necessary while the corn was growing. 

Considering the importance of this item of expense, 
and the fact that the sort of cultivation that was once 
practiced in corn growing is now almost wholly dis- 
carded, we may well consider what is the real purpose 



STUDIES ABOUT CROPS 65 

of the work given to the cultivation of corn and what 
would result if some or all of this work were omitted. 

In Exercise 28 the difference in the treatments of 
plots 1 and 3 is to see whether the early preparation 
of the soil, as in plot 1, will result in storing a larg( 
supply of water in the soil to the advantage of the cro]) 
so as to make it profitable to apply this extra labor. 

In plot 2, compared with 1, and plot 4, compared 
with 3, the test is made to see whether the frequent 
cultivations usually given to the corn field are valuable 
because they destroy the weeds or because they stir the 
surface soil. 

And the treatment of plot 5, when the results are 
compared with those of plots 3 and 4, should show 
whether it is very important to keep the weeds from 
growing with the crop. 

This work should be repeated each year, recording 
the results together with the special weather conditions 
of the season. If a number of schools in the country 
carry on the same experiment, there will be increased 
interest and value in the results obtained. 

References : Hunt, The Cereals in America, pp. 218-225. 
Orange Judd Co., The Book of Corn, pp. 87-95, 115-127, 167-191. 

Exercise 28 

Crop Production : Corn 

To SHOW Effects of Different Methods of Tillage 

Use 5 plots of one square rod each (^ rod X 2 rods), planting 
on each plot 3 rows of corn, running lengthwise of the plots, 3 feet 



66 MANUAL OF AGRICULTURE 

apart, the hills being 3^ feet apart in the row, 3 stalks to each 
hill. 

Prepare the soil for planting as follows : — 

Plot L Plow (or spade) as early in the spring as the soil is in 
condition to work, and thoroughly cultivate the surface each week 
until the time of planting. Keep the plot free from weeds, and a 
loose surface mulch until the ground is thoroughly shaded by the 
corn. 

Plot 2. Prepare the ground for planting as in plot 1, but after 
the corn is planted do not stir the ground at all. Keep the weeds 
down by shaving them off with a sharp hoe. 

Plot 3. Do not plow (or spade) the ground until just before 
planting. Then cultivate the plot through the season carefully, as 
in the case of plot 1. 

Plot 4. Do not prepare the ground until ready for planting. 
After planting, treat the plot in the same way as was done with 
plot 2, merely shaving off the weeds at the surface. 

Plot 5. Prepare the ground for planting as was done for plots 
3 and 4. After planting, do nothing more, allowing the weeds to 
grow and the soil to remain packed and uncultivated. 

During the season make notes from time to time of the appear- 
ance of the crops on each plot. Take measurements of the height 
of plants and record them and other evidences of relative vigor of 
the crops on each plot. Where were the signs of lack of sufficient 
moisture most apparent ? 

At the proper season husk the corn on each plot, weigh and re- 
cord the crops, reducing them to acre equivalents. 

XXVI. — How Moisture may be saved for the 
Corn Crop 

It is the general belief that one of the chief benefits 
resulting to the crop from the frequent stirring of the 



STUDIES ABOUT CROPS 67 

surface of the soil is due to the conservation of the mois- 
ture content of the soil by means of the loose dust mulch. 

The tests to be made in Exercise 29 are to determine 
how great are the differences in the amounts of water 
stored in the upper 40 inches of the soil due to the 
various cultural treatments that were used. 

The differences in the amounts of water found on the 
several plots should be expressed in acre-inches and 
tons per acre. 

Reference : Hunt, The Cereals in America^ pp. 235-242. 

Exercise 29 

Determination of the Water Coyitent of the Soil on Each 
Plot for Exercise 28 

Mark and weigh 30 soil pans, as in Exercises 2 and 3. (Run 
the determinations in dupHcates.) Takes samples of surface, sub- 
surface, and subsoil from each plot according to directions for Ex- 
ercise 2. Weigh out 100 grams of soil in each pan, and let them 
dry at room temperature for a week. Weigh again, and the loss of 
weight will be the number of grams of capillary moisture con- 
tained in the soil. A comparison of the amounts of water found 
in the soils of the different plots will impress the value of tillage in 
the conservation of moisture. 

Do the results show the value of preparing the ground for the 
crop as early as possible? 

How much water has been stolen from the plots by the weeds ? 

XXVII. — Growth of Corn Roots 
By far the greater part of the labor expended in 
growing the cereal crops is directed to bettering those 



68 MANUAL OF AGRICULTURE 

conditions which affect the environment of the roots, 
and yet this is the part of the plant about which farmers 
generally have the most indefinite and incorrect con- 
ceptions. 

The root naturally is the least conspicuous portion 
of the plant, and it is difficult to remove it from the 
soil without leaving behind so much of the delicate 
fibers and root hairs tliat one usually gets a very imper- 
fect conception of the position which a plant's roots 
occupy in the soil and the extent of area that they 
cover. 

To those who have not investigated this subject, it 
will be a surprise to learn how rapidly corn roots grow 
in a fertile soil and how soon they spread laterally to 
the center of the rows. 

How deep the cultivation can safely be made between 
the rows of corn, and how close to the hill it is wise to 
stir the soil, even to the depth of two or three inches? 
are questions about which farmers differ. 

Exercise 30 is given for the purpose of directing at- 
tention to a more thorough study of the root systems of 
plants and the habits of root growth, in order that the 
farmer may possess some reasonable basis for his deci- 
sions in the matter of the cultivation of his crops. 

Such exercises as this will necessarily extend into the 
summer vacation ; but some pupils in some schools 
may become so interested that they will want to carry 
on the investigation during the summer and make their 
reports at the opening of the next year of school. In 
fact, an interest which will carry this work into the 



STUDIES ABOUT CROPS 69 

homes of tli3 pupils and connect it with the work on 
the farm and in the garden must be the real test of the 
school's success in teaching agriculture. 

References : Hunt, The Cereals in America^ pp. 336-340, Orange 
Judd Co., Tlie Book of Corn, pp. 115-127. 



Exercise 30 

Crop Production: Corn 

A Study of Corn Roots 

Plant one plot of corn to be used for the purpose of investiga- 
tions of the roots and the effects of deep and shallow cultivation. 

Beginning one week after the corn appears above the ground, 
carefully remove a hill so as to preserve all the roots, wash the 
soil off, and examine the growth of the roots. How wide an area 
do they occupy in the ground 1 How near the surface do they 
lie at 4 inches' distance from the hill ? How near the surface are 
they at distances of 6 inches and 1 2 inches from the hill ? 

Once each week for the first six or eight weeks after planting, 
try to examine the roots of a hill of corn and take measurements 
of the spread and depth they have made, and their nearness to the 
surface at 4, 6, and 12 inches from the hill. This experiment re- 
quires considerable manual labor and patience to carry it through 
so that it shall have value. Each week it will be necessary to dig 
a deeper trench about the hill of corn and use more care to remove 
the soil without injuring the roots. However, it is of great im- 
portance to the corn growers to know how the roots of the corn 
plant develop and just how they lie beneath the surface. 

To test the effects of deep cultivation, in which the roots of the 
corn plant are cut off, a simple tool can be made by fastening a 



70 MANUAL OF AGRICULTURE 

handle to a solid block of wood about 6 inches square and 2 inches 
thick; then get a blacksmith to make a thin steel blade with 
three holes, so that it can be screwed to the block in such a way 
that it will project below two, four, or six inches, as desired. With 
this implement it is possible to run along the side of a row and 
prune the corn roots at any one of these three depths. A strip of 
lath fastened to the top of the block and extending to one side will 
keep the knife at the desired distance from the hill. 

This pruning of the roots may also be done with a spade by 
tightly bolting two strips of wood on each side of the blade to serve 
as guards, and control the depth to which it can be thrust into the 
ground. By loosening the bolt at the ends of the strips, the guards 
may be raised or lowered. 

Select a plot where the corn is of uniform growth. Lay off 8 
rows, each containing 25 hills, and treat each row according to the 
following directions : — 

Row 1. Shallow cultivation with a garden rake. 

Row 2. Roots pruned 4 inches from hill and 2 inches deep. 

Row 3. Roots pruned 4 inches from hill and 4 inches deep. 

Row 4. Roots pruned 4 inches from hill and 6 inches deep. 

Row 5. Roots pruned 8 inches from hill and 4 inches deep. 

Row 6. Roots pruned 8 inches from hill and 6 inches deep. 

Row 7. Shallow cultivation with garden rake. 

The cultivation and pruning should be the same on all four sides 
of each hill. 

The pruning should be done whenever the corn is cultivated, 
for the purpose of the experiment is to compare the results from 
deep and shallow cultivation in ordinary farm practice. 

After each pruning of the roots, observe whether any of the 
rows wilt or show injury. 

T^ake measurements of the growth in height of different rows. 
At husking time, harvest and weigh the corn from each row sepa- 



STUDIES ABOUT CROPS 71 

rately and record the results. Make a written statement of the 
conclusions reached by this experiment. 



Exercise 31 

Corn Breeding : Selection of Seed 

The purpose of this exercise is to impress upon the minds of the 
students the fact that individual characters of plants are trans- 
mitted from parent to offspring, as in the case of animals ; and 
therefore, by selection of seed, the plant breeder may exercise large 
control in securing desired qualities in the crops that he raises. 

Get permission from some farmer for the class in agriculture to 
go through his corn field in the early part of September and mark 
certain plants that show striking individual characters. For in- 
stance, find a corn plant that bears its ear very high on the stalk, 
and another plant equally vigorous that carries its ear lower than 
the average plants. Record the height of each ear. 

Mark two other plants, one of which has two good ears, while 
the second has but one. Again, select a corn plant that is firmly 
rooted and stands erect ; and in contrast, a plant that is weak in 
its root and has fallen down. Also find a plant that shows a 
strong tendency to " sucker," and another free from suckers. 

When the com is fully mature, secure from the farmer the ears 
on the plants that you have marked, carefully number or label 
them, and record the special characteristic for which the plant was 
selected. Also select two ears from the crib of the same variety 
which have kernels of distinctly different types, one square in 
shape and the other rounded. 

This will give ten ears for the experiment. Now, if possible, 
lay off a plot 2 rods X 5 rods, which will permit of 10 rows, each 



72 MANUAL OF AGRICULTURE 

having 25 hills. Plant each row from the seed of a single ear as 
follows : — 

Row 1. Character: high ear. 

Row 2. Character : low ear. 

Row 3. Character : two ears to a stalk. 

Row 4. Character : single ear to a stalk. 

Row 5. Character : strong, erect stalk. 

Row 6. Character : weak, prostrate stalk. 

Row 7. Character : tendency to produce suckers. 

Row 8. Character : free from suckers. 

Row 9. Character : square-shaped kernels. 

Row 10. Character: round-shaped kernels. 

Give the same treatment to all the rows ; observe during the 
season whether the plants of any of the rows show peculiarities of 
growth corresponding to the parent plant, and make a record of 
what you observe. 

At the end of the season tabulate the results of the experiment 
as follows : — 

Row 1. Average height of ears. 

Row 2. Average height of ears. 

Difference between the average heights of the high and the low 
ears. 

Compare the average height of the high ears with height of the 
seed ear. 

Compare the average height of the low ears with the height of 
the seed ear. 

Row 3. What per cent of the plants have more than one ear ? 

Row 4. What per cent of the plants have more than one ear ? 

Row 5. What per cent of the plants stand erect ? 

Row 6. What per cent of the plants stand erect ? 

Row 7. What per cent of the plants have suckers? 

Row 8. What per cent of the plants have suckers ? 



STUDIES ABOUT CROPS 73 

Row 9. What per cent of the ears have square kernels ? 
Row 10. What per cent of the ears have round kernels? 



Exercise 32 

Corn Breeding : Practice in Detasseling 

Prepare a plot of ground (2 rods wide and of any length) for 
an experiment in corn breeding. This width of plot will allow for 
10 rows, and the hills should be 3^ feet apart in the row. 

Use as seed the best ten ears of corn that you can get. Num- 
ber the ears and the rows, and plant each row with seed from the 
ear of corresponding number. As soon as the tassels begin to ap- 
pear, they should be removed from all the plants in every alternate 
row. 

The work of detasseling is performed in this way : The tassels 
should not be cut off, as that is likely to injure the plant ; but as 
soon as the tassel is sufficiently developed, and before the pollen is 
matured, a careful pull will separate it from the stalk at the top 
joint. It will be necessary to go over the plot several times to 
make sure that every tassel is removed from these rows before they 
ripen their pollen, for the tassels wiU not appear on every plant at 
the same time. 

From the rows that are not detasseled remove all undesirable 
plants, i.e. (a) those that produce no ears ; (h) those that show a 
tendency to grow suckers ; (c) those that are weak in their roots ; 
and (c7) those that show any smut. 

Seed ears are to be selected only from the detasseled rows, be- 
cause with these plants there is absolute certainty that every ker- 
nel has been produced by cross-pollination. 

This exercise is given mainly to furnish practice in the method 
that is generally followed now by breeders of pedigreed seed corn. 



74 MANUAL OF AGRICULTURE 

Harvest and weigh the corn from each row separately, and keep 
a record of results. If it is possible to continue this experiment 
from year to year, select the seed to be used the following year 
from the highest-yielding rows that were detasseled. Observe 
whether detasseling seems to increase or decrease the yield as com- 
pared with the rows bearing tassels. 



Exercise 33 
Experiment in Hand Pollination 

In order to be certain in regard to both sire and dam in the 
production of seed, it is necessary to protect the pistils of the plants 
that are to bear the seed from any possible contact with the pol- 
len grains of their own stamens or of those of any other plants 
except the ones chosen for the sires. 

To do this in the case of corn, make a number of little bags of 
cotton cloth about 6 inches wide and 10 inches long. Narrow 
strips of the same cloth stitched in the middle to the edge of the 
mouth of the sack make convenient strings for holding the bags 
in place. 

Before any of the silk appears on the tips of the young ears 
that have been selected for the dams, draw over each of the ears 
one of the cloth bags and tie it securely about the shank of the 
ear. 

For mating with each dam, select the same number of corn plants 
to serve as sires, and as soon as the pollen on the tassels of these 
plants becomes mature and begins to shed, shake it off carefully 
from one of the plants into an open dish ; now remove the sack 
from the ear of one of the dams and rub the ends of the silks care- 
fully in the pollen that has been collected in the bottom of the 
dish, making sure that every one of the silks comes in contact with 



STUDIES ABOUT CROPS 75 

a grain of the pollen. Then replace the sack over the end of the 
ear, and do not remove it again until two or three weeks later. 

To determine the difference in the vigor of seed produced by 
cross-poUination from that resulting from self-pollination (pistils 
fertilized by the pollen of the same plant), pollinate the silks of 
three or four ears with pollen taken from the tassels of the same 
plants. Mark the ears thus produced, and the following year plant 
a few rows with seed from these ears by the side of rows where 
cross-pollinated seed was used, and compare results. 

Cross-pollinate the silk of an ear of white corn with the pollen 
from the tassel of yellow corn, and vice versa. What is the color 
of the cob grown on the stalk of white corn ? What is the color 
of the grain on this ear 1 What is the color of the cob on the stalk 
of yellow corn 1 What is the color of the grain ? 

On one ear do not remove the sack nor apply pollen to the silk. 
After several weeks take off the sack, and notice how long the silk 
has grown. What does this teach 1 

XXVIII. — Observation Studies in the Cornfield 

The development of the present breeds of cattle and 
other live stock plainly shows how careful, systematic, 
and intelligent selection has improved the animals. 
Plants respond to breeding and selection as readily as 
do animals, and there is no longer any doubt that va- 
rieties of corn may be further improved by similar 
methods. Experiments conducted by the Illinois Ag- 
ricultural Experiment Station and other similar insti- 
tutions have conclusively shown that the composition 
of the corn kernel may be varied at the will of the careful 
breeder ; that it is possible to increase or decrease the 



76 MANUAL OF AGRICULTURE 

amount of oil, or of starch, or of protein by selection of 
seed. 

It is equally true that greater variations may be 
made in the ears or the stalks by selection.' The 
amount of husks, length of shank, size, and height of 
stalk, position of ear on the stalk, the number of leaves, 
and in fact every physical characteristic, can be varied 
in a short time by simple selection. It is just as im- 
portant to know the character of every part of the corn 
plant as to know every characteristic of the animal. 
The size, shape, and characteristic of the stalk strongly 
influence the development of the ear and kernel of corn. 

Get permission from a farmer whose land is conven- 
ient to the school to use his cornfield for the purpose of 
making a study of the corn crop. Have each pupil 
work on separate plots, ten hills square, and make his 
notes and records with reference to the following 
points : — 

Exercise 34 
Field Work with Corn 

Name of variety Size of field 

1. Date the corn matures : (a) roasting ear : 

(6) dented or glazed (c) ripe 

2. Height of corn ; average of ten plants feet 

inches 

3. Total number of leaves on ten plants, taken from different hills 
Average number of leaves per plant 

4. Total number of leaves below the ear on ten plants, taken from 
different hills Average 



STUDIES ABOUT CROPS 77 

5. Figure the total leaf surface on five average corn plants (for each 
leaf blade take twice the product of the length and average width) 



6. Length of ear stem, or shank (distance from joint, or node, to 
base of ear) . Average of ten plants 

7. The ear stem, or shank, may be (1) large^ — nearly or quite 
the diameter of the cob ; (2) medium^ — or about half the diameter of 
the cob ; (3) small, — or one third or less the diameter of the cob. 

8. Husks: abundant, medium, scarce 

9. Husks: close, medium, loose 

10. Measure ten hills square ; give number of ears on these one 
hundred hills Average per hill 

11. Give number of stalks in the above area having two or more 
ears 

12. Give number of stalks in above area without ears (barren 
stalks) 

13. Give average height of ears in above area 

14. Position of the ears on stalks : pointing upward ; horizontal ; 
pointing downward 

15. Distance apart of hills each way 

16. Give number of hills per acre 

17. Measure off one acre which represents a good average of the 
field ; husk one twentieth of this, and after weighing same carefully, 
estimate the average yield of field 

18. If hills of corn are 3 feet 6 inches each way, how many hills 
to the acre ? 

19. If, in a field of corn planted 3 feet 6 inches each way, there is 
on the average 1| pounds of corn to each hill, counting 80 pounds to 
the bushel to allow for shrinkage, what is the yield per acre ? 

20. If corn is planted 3 feet 6 inches each way, and when mature 
is cut and put into shocks, each shock containing the corn from an area 
14 hills square, how many shocks to the acre ? 

How many of the shocks are 16 hills square ? 



78 MANUAL OF AGRICULTURE 

The following table will assist in making accurate estimate of 
the amount of land in different fields or plots : — 

10 rods X 16 rods = 1 acre. 220 feet x 198 feet = 1 acre. 

8 rods X 20 rods = 1 acre. 440 feet x 99 feet = 1 acre. 

5 rods X 32 rods = 1 acre. 110 feet x 396 feet = 1 acre. 

4 rods X 40 rods = 1 acre. 60 feet x 726 feet = 1 acre. 

5 yards x 968 yards = 1 acre. 120 feet x 363 feet = 1 acre. 
10 yards x 484 yards = 1 acre. 240 feet x 181.5 feet = 1 acre. 
20 yards x 242 yards = 1 acre. 200 feet x 108.9 feet = ^ acre. 
40 yards x 121 yards = 1 acre. 100 feet x 145.2 feet = | acre. 
80 yards x 60^ yards = 1 acre. 100 feet x 108.9 feet = I acre. 

Area of One Acre 

10 square chains = 1 acre. 

160 square rods = 1 acre. 

4,840 square yards = 1 acre. 

43,560 square feet = 1 acre. 

640 acres = 1 square mile. 
36 square miles (six miles square) = 1 township. 



Exercise 35 

Studies of an Ear of Corn 

In order to become accustomed to the essential points in study- 
ing the characteristics of corn, the following suggestions are ap- 
pended. Take ten ears each of two or more different varieties, 
preferably one yellow, one white, selecting ears as uniform and 
true to the variety type as possible. To get a close comparative 
study, it is advisable to lay all the samples on a table side by side. 
After studying the characteristics carefully, use this list for refer- 
ence and bring out by example the points mentioned; then the 
work of scoring the samples may be taken up, following carefully 
the several points indicated on the corn score card as given on 



STUDIES ABOUT CROPS 79 

page 84 of this manual, and noting carefully the explanatory notes. 
Each sample of ten ears should be marked and known as " Ex- 
hibit A," " Exhibit B," etc. The letters (a) and {b), as used below, 
refer to the sample under examination, and it is intended that the 
corresponding characteristics possessed by each variety be marked 
in the blank space. 

Name of variety (a) (h) 

I. Color of grain: white; yellow; golden, (a) (6) . 

II. Color of cob : white ; light red ; dark red. (a) (b) 

III. Surface of ear : smooth; rough; veiy rough, (a) 

(6) 

IV. Rows of kernels : — 

1. Are rows in distinct pairs (alternate spaces between rows of 
kernels wider than the others) ? (n) (&) 

2. Number of rows (count three inches from butt), (a) 

(&) 

3. Number of rows lost (disappearing after extending three inches 
or more from butt), (a) (&) . 

4. Spaces between rows: medium; narrow; wide, (a) 

(6) 

5. Are rows straight (parallel with cob) ? (a) (&) 



6. Are rows turned to the right or left (twisted to right or left 
of a straight line from butt to tip) ? (a) (p) 

V. Grains on cob : dovetailed or mosaic-like ; firm ; loose ; very 
loose: (a) (&) 

VI. Shape of ears : — 

1. Cylindrical (uniform in circumference from butt to tip), (a) 
(5) 



80 MANUAL OF AGRICULTURE 

2. Partly cylindrical (uniform in circumference for a portion of 
length, (a) (6) 

3. Slightly tapering (taper slight and regular), (a) 

(6) 

4. Distinctly tapering (taper very apparent), (a) 

(&) 

5. Very tapering (extremely tapering), (a) (6) 

6. Are the ears in the exhibit too short or too long for their cir- 
cumference ? (The proper proportion is for northern Illinois, 6.75- 
7.50 inches in circumference to 9-10 inches in length ; for central and 
southern Illinois, 7-7.75 inches in circumference to 10-11 inches in 
length), (a) (b) 

VII. Butts of ears : — 

1. Even (entire end of cob exposed, with butt kernels at right 
angles to axis of cob) . (a) (6) 

2. Shallow rounded (cavity at butt shallow, broad), (a) 

(6) 

3. Moderately rounded (cavity moderately deep, medium diam- 
eter), (a) (a) 

4. Well rounded (cavity at butt deep, small diameter where 
the shank is removed, rows of grains extending in regular order over 
the butt), (a) (6) 

6. Compressed (cob rounded at end ; kernels at butt fiat, smooth 
and short, indicating a tight husk), (a) (b) 

6. Enlarged (large butt with no extra rows of kernels), 
(a) (6) 

7. Expanded (large butt caused by extra rows of kernels). 
(«) (b) 



STUDIES ABOUT CROPS 81 

VIII. Tips of ears : — 

1. Kernels in rows (rows may be traced to tip), (a) . 

(&) 

2. Flat (cob flattened at tip), (a) (&) 

3. Filled (entire end of cob covered with kernels) . (a) 

(6) 

4. Capped (a central kernel projecting from filled tip) . (a) 

(&) 

IX. Kernels : — 

1. Firm (rigid on cob), (a) (6) 



2. Loose (movable on cob), (a) (6) 

3. Upright (at right angles with surface of cob), (a) 

(6) 

4. Sloping (leaning toward tip.) (a) (6) 

6. Square at top (corners not rounded at summit), (a) 

(6) 

6. Shoe-peg form (long, narrow kernel holding size to tip) . 
(a) (6) 

7. Rounded corners (corners rounded at summit and base), 
(a) (6) 

8. Beaked (with long, sharp, tapering projection), (a) 

(6) 

X. Junction of ear stem, or shank, with ear : large ; medium ; 

small, (a) (&) 

XL Average length of ears : (a) (6) 



XIL Average circumference of ears one-third distance from butt; 
(«) (&) 



82 MANUAL OF AGRICULTURE 

XIII. Give ratio of circumference of average ear to length of aver- 
age ear (divide length of ear by circumference of ear) . [The proper 
proportion of circumference to length is as 3 to 4 ; or for medium 
varieties 7.5 to 10 inches.] (a) (b) 

XIV. Weigh five ears from each sample, taking each alternate ear ; 
give average weight of ears, (a) (&) 

XV. Shell these five ears and give average weight of cobs, 
(a) (&) 

XVI. Give average circumference of cobs one-third distance from 
butt, (a) (5) 

XVII. Give ratio of circumference of average cob to average ear 

(divide circumference of ear by circumference of cob) . (a) 

(b) 

XVIII. Give percentage of grain : [Note. — To determine the per- 
centage or proportion of grain to cob, select every alternate ear in the 
exhibit and weigh same. Shell and weigh the cobs; subtract the 
weight of the cobs from the total weight of the ears, giving weight of 
shelled corn. Divide the weight of shelled corn by the total weight of 
ears, which will give the per cent of grain. The per cent of grain 
should be from 86 to 90. ] (a) (6) 

XIX. Count the number of kernels of corn on the largest ear and 
on the smallest ear in each exhibit, (a) (b) 

XXIX. — Judging and Scoring Corn 

The object of corn judginc^, like that of stock judg- 
ing, is to iix more clearly in the mind certain ideals of 
excellence which shall serve as standards of comparison 
to aid in the improvement of the products we are work- 
ing to secure. 



STUDIES ABOUT CROPS 83 

It is to the interest of the corn grower to produce the 
largest yields and the best quality of this grain at the 
greatest profit. 

The careful study of corn has taught that certain 
characters of ear and kernel are closely associated with 
large yields and high quality. Taking these as the 
basis for a standard of perfection, the Illinois Corn 
Growers' Association has formulated a score card on 
which are indicated the several points to be considered 
in estimating the merits of a sample of corn and the 
relative degrees of importance of these points. 

It has been found that the use of such a score card is 
a valuable aid to the judge or students in comparing 
and determining the relative merits of several samples 
of corn. 

CORN SCORE CARD 
Name of Scorer Date 



Post Office Exhibit No.. 

Standard Measurements of Variety 

Name of Variety 

Length 

Circumference . 

Proportion of Grain to Cob 



The Corn Score Card 

The following is the score card of the Illinois Corn Growers' 
Association, as revised and adopted by that Association January 
29, 1908. This should be used in judging varieties or samples 
not named, and also where the exhibit is not made under a variety 
classification. 



84 MANUAL OF AGRICULTURE 

Measurements for General Score Card 



Northern Illinois . . . . 
Central and southern Illinois 



Length. 
Inches. 



9-10 
10-11 



Circumfer- 
ence. 
Inches. 



6.75-7.50 
7.00-7.75 



Proportion 
OF Corn 
TO Cob. 



88 per cent 
88 per cent 



Points. 



Perfect 
Score. 



Score of 
Sample. 



1. Uniformity of exhibit .... 

2. Shape of ear 

3. Length of ear 

4. Circumference of ear .... 
6. Tips of ear 

6. Butts of ear 

7. Kernel uniformity 

8. Kernel shape 

9. Color in grain and cob .... 

10. Space between rows .... 

11. Space between kernels at cob 

12. Vitality or seed condition . . . 

13. Trueness to type 

14. Proportion of shelled corn to cob 

Total 



b 
10 
10 
5 
5 
5 
5 
5 

10 
5 
5 
10 
10 
10 

100 



Explanation of Points 

1. Uniformity of exhibit : uniform in shape, length, and circumfer- 
ence. 

2. Shape of ears : ears cylindrical, with straight rows and with 
proper proportion of length and circumference. 

3. Length of ears : varies with variety measure. 

4. Circumference of ears : varies with the variety measure. 



STUDIES ABOUT CROPS 85 

5. iTips of ears : oval shape and regularly filled out with large, 
dented kernels. 

6. Butts of ears : kernels rounded over the end of the cob in regular 
manner, leaving a deep depression when shank is removed. 

7. Kernel uniformity : kernels from the same ear and from the sev- 
eral ears uniform in size and shape. 

8. Kernel shape : kernels deep, wedge-shaped, full at germ end. 

9. Color : free from mixture and true to variety color. 

10. Space between rows : furrow between rows and space caused by 
round corners of kernels, which should be narrow, deep, and sufficient for 
perfect ventilation. 

11. Space between kernels at cob : space in row between kernels at 
cob. 

12. Vitality or seed condition: ripe, sound, dry, and of strong vitality. 
Grains of a pinkish color objectionable. Three dead ears shall disqualify 
an entire exhibit. 

13. Trueness to type : conforming to variety characteristics in variety 
classes, and to the prevailing type in general classes. 

14. Proportion shelled corn to ear. 

Explanatory : How to study and apply the Points of the 
Score Card 

Note A. — In all exhibits made prior to November 15 of each year, 
all standards of length and circumference shall be increased one-half 
inch, and standards of per cent shall be reduced two. 

Note B. — The length and circumference of the general score card, 
for the northern district, shall be used in judging the standard varie- 
ties, when shown within that district of the state. 

Note C. — Exhibitors may remove two kernels side by side from the 
same row at the middle of the ear for kernel examination. 

1. The deficiency and excess in length of all ears shall be added 
together, and for every inch thus obtained, a cut of one point shall be 
made. Should the deficiency in length exceed ten inches, a cut of 
two points for each additional inch shall be made on the total score. 
In determining length, measure from the extreme tip to the extreme 
butt. 

1 It is recommended that judges interpret this rule very liberally, 
and that tips be not heavily cut for slight deficiency, so far as being 
filled over with kernel is concerned. 



86 



MANUAL OF AGRICULTURE 



2. The deficiency and excess in circumference of all ears not con- 
forming to the standard of the variety shall be added together, and 
for every inch thus obtained, a cut of one point shall be made. Meas- 
ure the circumference at about one-third the distance from the butt to 
the tip of the ear. 

3. In determining the proportion of corn to cob, weigh each alter- 
nate ear in the exhibit. Shell and weigh the cobs, and subtract from 
weight of ears, giving weight of corn. Divide the weight of corn by 
the total weight of ears, to get the per cent of corn. For each per cent 
short of the standard for the variety, a one-point cut shall be made. 

4. In judging color, a red cob in white corn or a white cob in yellow 
corn shall be cut ten points. For one mixed kernel, a cut of one-fifth 
of a point shall be made ; for two, two-fifths of a point ; for three, three- 
fifths of a point; for four, four-fifths of a point; for five or more, a 
one-point cut shall be made. Kernels missing from the ear shall be 
counted as mixed, at the discretion of the judge. Difference in shad© 
of color of grain or cob shall be scored according to variety character- 
istics. 

Measurements for Named Varieties 

Certain varieties of corn have been grown and bred for a long time 
by men who by improved methods have developed certain character- 
istics of stalk and ear, such as color and shape of kernel, shape and 
size of ear, maturity, etc. Furthermore, each variety has its peculiar 
length, circumference, and proportion of com to cob. Based on a 
careful study of the best samples of the different varieties recognized 
by the Illinois Corn Growers' Association, these variety standards are 
as follows : — 



Reid's Yellow Dent . 
Leaming .... 
Boone County White 
Riley's Favorite . . 
Golden Eagle . . . 
Silver Mine .... 
Champion White Pearl 



Length. 



10 to 11 in. 
10 to 11 in. 
10 to 11 in. 

9 to 10 in. 

9 to 10 in. 

9 to 10 in. 

8 to 9 in. 



Circumference. 



7 to 7.75 in. 
7 to 7.75 in. 
7 to 7.75 in. 
6.75 to 7.5 in. 
7 to 7.75 in. 
6.75 to 7.5 in. 
6.75 to 7.5 in. 



Pee Cent of 
Corn to Cob. 



88 
88 
88 
90 
90 
90 
85 



STUDIES ABOUT CROPS 87 

Suggestions for preparing Exhibit 

In judging corn, ten ears usually constitute an exhibit sample. It is 
desirable that samples be laid out side by side on a table where a good 
light may be had. 

There is no better way to sort and select seed corn or to prepare a 
sample for exhibition than to place the ears from a bushel or so of 
selected corn upon a board or table, with the tips all pointing one way. 
Select the most perfect ear you can find, something which is your ideal 
type. Then, with this ear in your left hand, go over all the ears of 
corn upon the table, discarding those showing too great a variation 
from type in size, length, shape, roughness, and the size, shape, and 
indentation of kernel, etc. 

In preparing corn for exhibition, the ears should be groomed so as 
to present the best possible appearance by removing all husk, silks, and 
shanks, but do not mutilate or cut the ear itself in any way. Neither 
is it allowable to remove mixed kernels and substitute kernels of a 
proper color. The ears should be handled carefully, that no kernels be 
knocked off, for kernels that are missing are usually regarded as mixed, 
and the usual cut made for such imperfection. If the exhibit is to be 
sent away, each ear should be carefully wrapped in a piece of newspa- 
per or other protection and firmly packed in a box. 

Note A. — The score card cannot be used in absolutely mathemati- 
cal sense. No set rules can be given ; it is largely a matter of the 
exercise of good sound judgment and patient practice on the part of 
the scorer. Where the number of points to be cut is not fixed by 
rules for judging, such as circumference, length, etc., the cut made 
should be in accordance to the degree of variance of each ear from 
value of the perfect ear, as fixed by standard. 

Remarks 

As has been said before, the score card is intended to be largely 
suggestive. It is not an infallible guide, but is to be used rather as a 
staff, or cane, as it were, to help us and to give a little more intelli- 
gent direction as to the essential points to be observed in selecting 
corn either for seed or for exhibition purposes. 

It should be borne in mind that while these ideal points and char- 
acteristics of the score card as described in the foregoing explanatory 



88 MANUAL OF AGRICULTURE 

notes are desirable, other things being equal, the lack of perfection 
may not prevent a variety from producing high yields or having in 
other particulars desirable qualities. For example, the cob should be 
neither too large nor too small. It is evident that of two ears of equal 
size and compactness, the one v^ith the small cob will have a deeper 
kernel and will contain more grain. On the other hand, while the 
small cobs may show a larger proportion of grain, yet the total weight 
of the ears may be much less and the yield per acre smaller, A large- 
sized cob is objectionable in that it usually carries a larger per cent of 
water, thus lowering the keeping quality of the grain and its vitality 
for seed. 

In a well-proportioned ear the shelled corn will occupy about the 
same space as did the ear before it was shelled. It is a good relation- 
ship where the depth of grain is one half the diameter of the cob, or 
the circumference of the ear twice that of the cob. 



Exercise 36 
Testing Corn for Seed 

The purpose in testing seeds is to determine, before planting, 
their vitality for germination and growth. 

Several simple devices are used for this work, the essential things 
being an arrangement for keeping the seeds exposed to the proper 
conditions of moisture and heat, and the grains from each ear 
separate, so that a record of every ear tested may be kept. 

The following method is recommended by the Agronomy De- 
partment at the University of Illinois : — 

Have a tinsmith make a galvanized tray 1 6 inches square and 2 
inches deep. Fill this tray with clean sawdust, thoroughly moistened 
before being placed in the tray, and pack it down firmly. If more 
convenient, use sand in place of sawdust. Cut a piece of white 
cotton cloth to fit inside the tray, and, with a ruler and good in- 
delible pencil, mark it off into squares of 1|- in. This will give 
100 squares, and 100 ears of corn may be tested at a time. 



STUDIES ABOUT CROPS 89 

Each square may be numbered, or the first square in each row. 
Have a pane of window glass of double thickness cut 15 J inches 
square, so that it will fit rather loosely into the tray. The ears 
to be tested should be numbered. This may be done by tying a 
tag to each ear or pinning it to the butt. 

When ready to fill the tester, take ear No. 1 in the left hand, 
and with the blade of a pocketknife pick out a kernel two inches 
from the butt. Lay this in square No. 1, germ side up. 

Turn the ear one fourth round and take a second kernel two inches 
nearer the tip, placing this grain also in the first square. In the 
same way, turning the ear one quarter of its circumference and 
moving two inches nearer the tip each time, select kernels three 
and four, the last being taken two inches from the tip end. Lay 
them all in the first square with their germ sides up. 

When the hundred squares are filled, each with four kernels, 
from ears numbered to correspond with the number of the square, 
lay the pane of glass carefully down on the grains so as not to 
move them from their places, and set the tray where the tempera- 
ture will range during the twenty-four hours from 60° to 80° F. 
Such conditions can generally be foimd in the family living room or 
near the furnace in the cellar. 

If the moist sawdust or sand is not packed into the tray until 
you are ready to place the grains in the tester, no more moisture 
will be needed. As the glass does not fit tightly in the tray, there 
will be suflBcient access of air for the seeds. 

AVithout removing the glass, it will be easy to see how the seeds 
are germinating. At the end of the sixth or seventh day, remove 
the glass and discard all kernels that have not put forth both a 
vigorous rootlet and a shoot an inch or more in length. No 
ear should be used for seed unless the four kernels germinate and 
show strong vitality. A class may work together on this exercise. 
Keep the records of all results. 



Jic 



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